OWNER’S MANUAL Traxxas Note: This manual covers TRX 3.3, TRX 2.5, and TRX 2.5R Racing Engines. Some photos 1100 Klein Road show the engine equipped with optional accessories, such as the EZ-Start system, headers, Plano, Texas 75074 and engine mounts, that are not included in the engine package. See the end panel of the Phone: 972-265-8000 engine box for exact contents based on your engine model number. Toll-free 1-888-TRAXXAS BEFORE YOU PROCEED Internet Traxxas.com Carefully read and follow all instructions in this and any accompanying materials to E-mail: [email protected] prevent serious damage to your engine. Failure to follow these instructions will be considered abuse and/or neglect. Entire contents ©2013 Before running your engine, look over this entire manual and examine the engine carefully. Traxxas. Traxxas, Top Fuel, If for some reason you decide it is not what you wanted, then do not continue any further. and Ready-To-Race are Your hobby dealer absolutely cannot accept an engine for return or exchange after it trademarks or registered trademarks of Traxxas. Other has been run. brand names and marks Warnings, Helpful Hints, & Cross-References are the property of their Throughout this manual, you’ll notice warnings and helpful hints identified by the icons respective holders and are used only for purposes of below. Be sure to read them! identification. No part of this manual may be reproduced An important warning about personal safety or avoiding or distributed in print or damage to your engine and related components. electronic media without the express written permission Special advice from Traxxas to make things easier and more fun. of Traxxas. Refers you to a page with a related topic.

2 • TRX ENGINES SUPPORT 4 SAFETY PRECAUTIONS If you have any questions about your engine or its operation, call the Traxxas Technical Support Line toll-free at: 1-888-TRAXXAS (1-888-872-9927)* 5 INTRODUCTION

Technical support is available Monday through Friday from 8:30am to 9:00pm central time. 6 TRX RACING Technical assistance is also available at Traxxas.com. You may also e-mail customer support ENGINE ILLUSTRATED with your question at [email protected]. Join thousands of registered members in our 7 TERMS TO KNOW online community at Traxxas.com. 11 THE FUEL Traxxas offers a full-service, on-site repair facility to handle any of your Traxxas service needs. Maintenance and replacement parts may be purchased directly from Traxxas by phone or 14 THE AIR FILTER online at BuyTraxxas.com. You can save time, along with shipping and handling costs, by 16 THE CARBURETOR purchasing replacement parts from your local dealer. 19 BREAKING-IN YOUR Do not hesitate to contact us with any of your product support needs. We want you to be TRX RACING ENGINE thoroughly satisfied with your new engine! 25 TUNING YOUR TRX REGISTERING YOUR MODEL RACING ENGINE In order to serve you better as our customer, please 29 TROUBLESHOOTING register your product within 10 days of your purchase YOUR TRX RACING ENGINE online at Traxxas.com/register. Traxxas.com/register 33 MAINTAINING AND STORING YOUR TRX RACING ENGINE

36 REBUILDING YOUR TRX RACING ENGINE

42 INDEX

*Toll-free support is available to U.S. residents only. TRX ENGINES • 3 SAFETY PRECAUTIONS

All instructions and SAFETY PRECAUTIONS precautions outlined All of us at Traxxas want you to safely enjoy your new TRX Racing Engine. Operate in this manual should be your TRX Racing Engine sensibly and with care, and it will be exciting, safe, and fun strictly followed to ensure for you and those around you. Failure to operate your TRX Racing Engine in a safe and safe operation of your responsible manner may result in property damage and serious injury. The precautions TRX Racing Engine. outlined in this manual should be strictly followed to help ensure safe operation. You alone must see that the instructions are followed and the precautions are adhered to. • Model engine fuel is dangerous and highly poisonous. Always follow all directions TRX Racing Engines and precautions printed on the fuel container. Model engine fuel is poisonous to are not intended for humans and animals. Drinking the fuel can cause blindness and death. Handle with use by children under 16 care and respect. years of age without the supervision of a responsible • Model engine fuel, especially when in a fuel dispensing bottle, may look like a cool and knowledgeable adult. drink to a child. Keep all fuel out of the reach of children at all times. Do not place fuel containers on the ground where children can reach them while you are driving. • Model engine fuel is flammable. Never allow smoking, sparks, heat, or flame in the presence of fuel or fuel vapors. • The engine and exhaust system may become extremely hot during use. Be careful not to touch these parts, especially when refueling or stopping the engine. • Prolonged exposure to the engine exhaust can be harmful. Avoid breathing the engine exhaust. Always run your nitro model outdoors, in a well-ventilated area. Never run the engine indoors. • The engine can be loud. If the noise makes you uncomfortable, wear ear protection. Be considerate of your neighbors by not running your model early in the morning or late in the evening. • Most importantly, use good common sense at all times. 4 • TRX ENGINES INTRODUCTION

INTRODUCTION Traxxas strongly TRX Racing Engines are the next generation of TRX nitro power. The larger displacement discourages changing and advanced porting generate class-leading horsepower while still maintaining the or modifying any part of TRX Racing Engine characteristics of broad, linear power delivery and ease of tuning. your TRX Racing Engine. Old Focused engineering and rigorous testing have yielded unprecedented power and tech tips and tricks that may have boosted the power of uncompromising performance that turns ready-to-run into Ready-To-Race®. other engines could seriously TRX Racing Engines take a total-system approach. Each part of the engine, from the air diminish the performance of filter to the exhaust tip, is carefully engineered to work in harmony with other engine your TRX Racing Engine. components. Each part complements the next, to extract maximum power. TRX Racing Engines are designed to be tolerant of variations in tuning and running through a wide There’s more advanced thinking, development, range of variable atmospheric conditions, such as changes in temperature, humidity, and and testing in the stock altitude. parts of your TRX Racing TRX Racing Engines are manufactured to exacting tolerances and require a specially- Engine than in many designed break-in procedure to accomplish the final precision fitting of the internal aftermarket manufacturer’s engine components. It is very important that you follow the new break-in procedure as so-called performance parts. TRX Racing Engines are closely as possible to achieve the best performance and longest life from your TRX Racing already some of the most Engine. Old style break-in procedures, such as simply running the engine with a very rich powerful engines in their fuel mixture for the first 4 tanks of fuel, will not achieve the best results. Follow the steps class and simply will not in this manual to successfully break in your TRX Racing Engine. benefit from average, low- A routine maintenance schedule is also required to keep your TRX Racing Engine in tech, aftermarket bolt-on performance items. top running condition. Cleaning the air filter after each hour of running is particularly important. Also, it is extremely important to perform after-run maintenance on the engine to prevent corrosion of the internal engine components (see page 34).

TRX ENGINES • 5 TRX RACING ENGINE ILLUSTRATED

Head Protector Air Filter Glow Plug Base PowerTune™ Head (Cylinder Head)

Pull Starter (if equipped) Idle Speed Air Filter Adjustment Screw Housing

High-Speed Needle

Fuel Intake Optional Air Intake Backplate (if equipped) Carburetor

Flywheel* Low-Speed Needle

Crankshaft Crankcase

Clutch Bell* Throttle Arm

6 • TRX ENGINES *not included (TRX 3.3 Engine shown. Other TRX Racing Engines are very similar.) TERMS TO KNOW TERMS TO KNOW Carb - Abbreviation for carburetor. You’ll find these Nitro R/C engine terms throughout this Carburetor - The carburetor atomizes (mixes) the fuel with section of the manual. the air so that the engine can burn it. There are two types .15 - .15 or “15” refers to the displacement of the engine. of carburetors; slide carbs and barrel carbs. TRX Racing The TRX 2.5 Racing Engine is .15 cubic inches or 2.5 cubic Engines use the superior slide carburetor design. centimeters (cc). The name “TRX 2.5” is derived from the cc Clean-out - Cleaning-out is a condition that occurs when measurement. the engine is accelerating and the fuel mixture becomes .20 - .20 or “20” refers to the displacement of the engine. The sufficiently lean to allow the engine to continue into its TRX 3.3 is .20 cubic inches or 3.3 cubic centimeters (cc). The upper RPM power band. It is usually characterized by a name “TRX 3.3” is derived from the cc measurement. noticeable decrease in blue exhaust smoke and a dramatic increase in engine speed. ABC - Abbreviation for aluminum, brass, and chrome. Refers to engine construction that consists of an aluminum Combustion chamber - The combustion chamber is piston that slides in a chrome-plated brass sleeve. machined into the bottom of the cylinder head. This is where the glow plug ignites the fuel. The shape of Air filter - The air filter sits atop the carburetor and prevents the combustion chamber is designed to promote more harmful dust and dirt from entering the engine. Dirt efficient burning of the fuel. ingestion is the number one cause of premature engine failure so the engine should never be run without the air Connecting rod - The connecting rod transfers the piston filter in place. motion to the crankshaft. TRX Racing Engines use a “knife- edged” connecting rod. The aerodynamic, sharpened BDC - Bottom dead center. The bottom-most position of the edges allow it to “slice” through the pressurized air/fuel engine piston stroke. mixture inside the crankcase. Break-in - Break-in is the procedure for running a brand new Crankcase - The engine’s “body” that contains all of the engine according to specific instructions. This correctly running mechanical components. prepares the engine for normal running. The break-in procedure can be different for different makes of engines. Crankshaft - The main shaft of the engine that holds the Follow the Traxxas directions for break-in exactly. reciprocating assembly. TRX ENGINES • 7 TERMS TO KNOW

Cooling fins - The cooling fins are milled into the cylinder Flame-out - Occurs when the engine stops running at high head and crankcase and cause heat to be drawn away RPM. Usually the fault of an excessively lean fuel mixture from the engine. Heat is removed when it dissipates into or glow plug failure. the air passing across the cooling fins. It is important to Fuel - (10%, 20%, 33%) TRX Racing Engines must have keep the fins clean of dirt and debris for maximum cooling model engine fuel to run. Traxxas Top Fuel® Power Plus™ efficiency. is recommended. Fuel is sold in quarts and gallons from Cylinder head (head) - The finned aluminum part on top of hobby dealers. The 10%, 20% and 33% labeling refers to the engine that is responsible for dissipating most of the the percentage of nitromethane contained in the fuel. engine’s heat. The combustion chamber is machined into Fuel mixture - The ratio of fuel to air as determined by the the bottom of the head. needle settings of the carburetor. Dyno - Abbreviation for dynamometer. A precise piece of Fuel tubing (fuel line) - The thick silicone tubing that carries testing equipment that accurately measures engine power fuel from the fuel tank to the carburetor. and torque output over the engine’s entire RPM range. Glow plug - The glow plug is located in the cylinder head EZ-Start - Traxxas on-board electric starting system. The at the top of the combustion chamber. It contains an system consists of a hand-held starter control unit and an element that glows red hot when voltage is applied. When on-board gearbox with an electric motor to spin the engine. the engine is being started, the heat from the glow plug Filter foam - The oiled foam element inside the air filter ignites the fuel mixture and starts the combustion process. housing. The filter foam in the engine must be thoroughly Glow plug driver - This tool clips onto the glow plug and cleaned and re-oiled after every hour of run time. supplies the required voltage to light the glow plug Fit - Usually refers to the fit of the piston and sleeve. If the element. It is also called an igniter. EZ-Start equipped fit is tight, the piston will feel very tight at the top of the engines do not require this separate tool. sleeve (top dead center), and the engine will have good Header - The aluminum tube that connects the exhaust sealing and compression. If the fit is loose, compression system to the engine exhaust port. The length and will be low and both the piston and sleeve should be diameter of the header must be carefully selected to replaced. extract the most power from the engine. TRX ENGINES • 8 TERMS TO KNOW

High-speed needle (HSN) - Needle valve that controls the Nitro content - The amount of nitromethane used in the fuel/air mixture at high throttle openings. fuel. Usually measured as a percentage of the total fuel Idle speed - The speed (RPM) the engine runs at when the volume. Traxxas engines are optimized to use 10-20% transmitter’s throttle trigger is at neutral. nitro. 33% nitro may be used for racing. Idle speed adjustment screw - Located on the carburetor Nitromethane - Nitromethane is a component in the fuel body. This screw adjusts the idle RPM of the engine. that increases power from the combustion process up to a point. Engines are generally optimized to use a range of Lean - A running condition in which the engine is not nitro content for the best power. getting enough fuel (for the available air). Symptoms include engine overheating, or the engine running for a O-ring - Rubber “O”-shaped ring used as a sealing gasket. short time and then stalling, particularly at high speed. Pipe - Abbreviation for the tuned exhaust pipe on a nitro This is a dangerous condition that should be corrected engine. See “Tuned Pipe”. immediately to avoid ruining the engine. Piston - The piston is the internal engine part that is Leaning the mixture - Turning either the high-speed and/or attached to the upper end of the connecting rod and low-speed needle(s) clockwise to decrease the amount of moves up and down in the cylinder sleeve. The precise fuel the engine receives. fit between the piston and the sleeve creates a seal that Low-speed needle (LSN) - Needle valve that controls the allows the engine to have the required compression for fuel/air mixture at low throttle openings. combustion. Needle valve - Valve consisting of a tapered needle that Port - Ports are openings in the sleeve that allow atomized closes against a corresponding seat to regulate fuel flow. fuel to enter the combustion chamber and burned exhaust gases to exit. The shape and location of the ports Nitro - Abbreviation for nitromethane, a component of are a large factor in controlling the engine timing and model engine fuel that improves fuel combustion and power output. power output. Nitro also refers to a class of R/C powered by model engines instead of electric.

TRX ENGINES • 9 TERMS TO KNOW

Priming - Manually causing fuel to move from the fuel Slide carburetor - The throttle on a slide carburetor closes tank up to the carburetor. This is sometimes necessary and opens by sliding a barrel in and out of the carburetor after the engine has been sitting for a long period of body. This type of carburetor is preferred for performance time and all of the fuel has drained back to the tank. On use because it provides a less restrictive “straight- a Traxxas model this is done by holding your finger over through” air path than the barrel carburetor design. the exhaust tip for one or two seconds while the engine Stall - When the engine stops running, usually due to an is starting. incorrect fuel mixture setting or running out of fuel. Punch - A term that refers to how quickly the model TDC - Top dead center. The top-most position of the responds to throttle input or how quickly it accelerates. engine piston stroke. Rich - A running condition where the engine is getting Tuned pipe - The tuned exhaust pipe usually consists of too much fuel for the available air. It is better to run an a specially-shaped metal or composite chamber with engine slightly rich to increase engine life. Excessively rich baffles that is designed to enhance the power output of mixtures cause the engine to have sluggish performance the engine. with exaggerated blue smoke and unburned fuel coming from the exhaust. Wear-in - Fitment process that occurs during engine break- in, in which internal engine parts develop an even more RPM - Abbreviation for revolutions per minute (how many precise matched fit through actual use under controlled times the engine crankshaft spins in a minute). circumstances. Sleeve - Internal engine part that contains the piston. The WOT - Abbreviation for wide-open throttle. precise fit between the sleeve and the piston creates a seal that allows the engine to have the required compression for combustion. The sleeve in a TRX engine is made of brass and is then hard-chrome plated.

TRX ENGINES • 10 THE FUEL

THE FUEL DANGER! Model engine Use the Right Fuel fuel is poisonous to It’s imperative that you use the correct fuel in your TRX Racing Engine for humans and animals. Drinking maximum performance and engine life. Traxxas Top Fuel™ should be used the fuel can cause blindness to ensure correct engine lubrication, performance, and ease of tuning. and death. Handle with care Traxxas Top Fuel has been proven in thousands of engines, so you can and respect. Keep it out of reach of small children at all count on it every day for great performance. times! While driving, do not • Top Fuel is the only fuel which is 100% certified for use in leave your fuel dispensing Traxxas engines. bottle on the ground where a child could have access to it. • Traxxas Top Fuel is made with just the right balance of the highest Follow fuel label warnings. grade natural and synthetic lubricants to allow excellent throttle response and the best top-end performance, without sacrificing long-term durability. • All of the components in the fuel are carefully selected from the best materials available and then custom blended to match the metallurgy and temperature characteristics of Traxxas engines. You may use 10%, 20% or 33% nitro-content fuel. Try to use the same percentage all the time, avoid switching back and forth between fuels. We recommend that if you break in your engine on 20% fuel that you stick with that percentage. If you do move to a higher or lower percentage, make sure you readjust your fuel mixture to compensate. Choosing a Nitro Percentage A commonly asked question is “what is the difference between 10%, 20%, and 33% fuels?” Increasing the nitro in the fuel is almost like adding extra oxygen to the combustion process. It burns more efficiently, improves combustion, and delivers more power. When increased nitro is used, more of the other fuel components are then required inside the combustion chamber to maintain the perfect air/fuel ratio. Therefore, overall fuel mixtures need to be richened slightly (on the high-speed needle, about 3/4 of a turn TRX ENGINES • 11 THE FUEL

counterclockwise when changing from 20% to 33%, about 1/2 of a turn counterclockwise when changing from 10% to 20%). This allows greater fuel flow through the engine and promotes cooler running, even at the maximum lean settings. If 33% improves power, then it seems that the highest nitro content available (beyond 33%) should always be used in the engine. In reality, there are practical limitations. Engines are designed to run best within a range of nitro percentages. How the engine is ported, the size of the combustion chamber and other factors determine how much nitro can be efficiently used in the engine. TRX Racing Engines respond exceptionally well to a maximum of 33% nitro, returning cooler temps, more power, and a smoother throttle response. For those who want to run higher nitro, 33% Top Fuel is the optimum nitro percentage for TRX Racing Engines. Increasing the nitro beyond 33% can introduce the need for engine modifications (ports, head shimming, etc.) to avoid starting and tuning difficulties. There are limits to how much nitro an engine can effectively use to make more power. Lower nitro percentages have their own advantages. Nitro is an expensive component in the fuel, so 10% nitro blend is more economical for the sport user. 10% also provides greater latitude with the needle settings for easier tuning. When using Traxxas Top Fuel, using higher nitro percentages does not cause the engine to wear out faster. 33% Top Fuel contains the same quality lubrication package as 10 and 20% Top Fuel. Some non-Traxxas high-percentage nitro racing fuels do sacrifice some lubrication in attempts to increase performance. We urge you to not take chances with your engine investment and use Top Fuel for consistent performance and long engine life.

12 • TRX ENGINES THE FUEL

Can other brands of fuel be used besides Top Fuel? There are other fuels that can provide satisfactory performance; however, there could be long-term costs in the form of decreased engine performance, loss of tuning ease, and shorter engine life. Only use fuels that contain both castor and synthetic oil. Everyone has an opinion or a claim to make about fuel. The engineering team at Traxxas has spent years developing TRX Racing Engines. No one knows more about the specific fuel requirements of Traxxas engines than Traxxas engineers. We strongly urge you not to take chances with your engine investment and use the Traxxas fuel made for TRX Racing Engines. Handling the Fuel • Follow all directions and warnings on the fuel container. • Keep the fuel tightly capped at all times. Some components in the fuel can evaporate very quickly and upset the balance of the fuel. • Do not store unused fuel in the fuel dispenser. Immediately return fresh unused fuel back into the fuel container. • Do not mix old and new fuel. Never mix different fuel brands together. • Store the fuel in a cool, dry location, away from any source of heat, ignition, or combustion. • Read and follow the safety precautions on page 4 in this manual.

TRX ENGINES • 13 THE AIR FILTER

Clean your air filter THE AIR FILTER after every hour of The TRX Racing Engine air filter is specifically designed to deliver maximum performance while run time to avoid engine protecting your engine from dust and dirt. Use only the supplied filter. You will not improve damage, even if the filter engine performance by switching to an aftermarket filter, and you may risk engine damage looks clean. due to poor filtration. The TRX Racing Engine air filter assembly consists of 3 pieces: If you use 1. A rubber filter base compressed air to 2. A plastic housing consisting of a permanently assembled mesh cap and body dry your air filter assembly, wear safety glasses and 3. An oiled foam element avoid directing compressed You must clean the filter after every hour of run time, even if the filter looks clean. This air toward your skin. includes the break-in time. Clean your air filter after break-in. Dust (which is often too fine to see) and dirt constantly move through the filter anytime the engine is running. Even if you can’t If foam filter oil is see dirt on the filter, it is present inside the foam after any amount of run time. If you exceed not available, clean the recommended cleaning intervals, your engine will be damaged. Engine damage or wear 30 or 40 weight motor oil due to dirt ingestion is easy to detect, and one of the top causes of premature engine failure. can be substituted, but is not preferred. Never Air Filter Cleaning Instructions run the engine without a 1. Remove the air filter from the carburetor bore by pulling the properly oiled filter! entire filter assembly firmly to the side to release it. Do not pull straight up. 2. Disassemble the filter. Pull the rubber air filter neck out of the filter body. With the base removed, the foam element is visible in the bottom of the filter body. Pull out the foam element. 3. Clean the filter parts by thoroughly washing all three pieces of the filter assembly in hot, soapy water (dishwashing detergent works well). Repeat twice. 14 • TRX ENGINES THE AIR FILTER 4. Thoroughly dry the parts with a clean towel or compressed air. Remember to wear your safety glasses when working with compressed air. 5. Oil the foam element with foam filter oil. Use the supplied Traxxas filter oil (part #5263) or a high-quality, special-purpose foam filter oil like that used for off-road motorcycle and ATV engines. This type of filter oil is available at motorcycle pro shops. Apply 30 drops of the Traxxas filter oil evenly to the top, bottom, and sides of the filter element (30 total drops divided among the 3 surfaces). Squeeze the filter element repeatedly to help spread the oil throughout. The filter element should be evenly colored by the oil. Even color indicates that the oil is distributed evenly. Do not squeeze out excess oil.

Note: Do not use the air filter oil for anything other than the air filter. It is not meant to be a lubricant. 6. Reassemble the filter and install it on the engine, making sure the rubber filter neck fits securely on the carburetor with no gaps or air leaks.

TRX ENGINES • 15 THE CARBURETOR THE CARBURETOR Factory Needle Understanding the carburetor adjustments Air Settings The carburetor performs several functions. If your factory preset It controls the engine’s speed by restricting Fuel carburetor adjustments the intake of air and fuel into the engine. It have been tampered with, atomizes the fuel (suspends the fuel droplets in use the following settings: the air) and also controls the air/fuel ratio of the mixture entering the engine (how much air for • Set the high-speed needle a given amount of fuel). To help provide a better to 4-turns out from closed. understanding of engine tuning and why it’s necessary, • Set the low-speed needle the following is a brief explanation of the air/fuel so the screw head (red in combustion process that takes place inside the engine. Fig. A) is flush (even) with the end of the slide (yellow In order to create the cylinder pressure that results in power, the engine burns the air/fuel mixture. Both air and fuel, in correct amounts, are needed for proper combustion. It is the in Fig. A). carburetor’s job to mix the air and fuel together (atomize the fuel), in the correct proportion Fig. A for the best possible combustion. This is the ideal air/fuel ratio required for the engine. The ideal air/fuel ratio remains roughly constant. Because of variations in atmospheric conditions (temperature, humidity, altitude, etc.), fuel flow adjustment valves (called fuel mixture needles) are required to meter the fuel and maintain the ideal air/fuel ratio in these ever-changing conditions. For example, colder air is more Low-Speed Cold Air (more dense) Warm Air (less dense) Needle Adjustment dense (more air molecules) for a given volume of air and therefore requires more Always use the factory fuel (more fuel molecules) to maintain the settings for initial starting. correct air/fuel ratio. Warmer air is less dense Only use these settings (fewer air molecules) and therefore needs less when the factory settings fuel to maintain the correct air/fuel ratio. The have been lost. tuning needles are there to adjust how much fuel is made available for the carburetor to mix with the available air (atomization). 16 • TRX ENGINES THE CARBURETOR

THE FUEL MIXTURE NEEDLES Richen See Tuning Your Water Valve The amount of fuel metered and atomized by (Controls Overall Flow) TRX Racing Engine, the carburetor is controlled by the two mixture High-Speed Needle starting on page 25, for needles: the high-speed needle and the low-speed complete information needle. The low-speed needle is used to meter on adjusting the air/fuel the fuel used by the engine at idle and low RPM mixture and idle speed. (part-throttle). The high-speed needle is used to meter the fuel when the throttle is open from part Water Nozzle A “turn” refers to throttle to wide-open throttle (WOT). These two (Controls Fine Flow) tightening (“turning needles provide precise control of the air/fuel ratio Low-Speed Needle in”) or loosening (“turning across the engine’s entire RPM range. out”) mixture needles. A The maximum possible fuel flow is always controlled by the high-speed needle. It works like the “full turn” refers to turning main water valve on a garden hose. Turn it clockwise to close the valve, counterclockwise to the needle 360°, so a “1/2- open it. When the throttle is at idle or partially open, the low-speed needle meters the fuel flow turn” would be 180°, a at the outlet (needle seat) where the fuel enters the carburetor venturi. This second valve acts “1/4-turn” would be 90°, like the spray nozzle at the end of the garden hose in our example. When you accelerate from and so on. idle, the throttle opens and the low-speed needle is pulled away from the needle seat. This Full Turn allows more fuel to flow with the increased air flow. As the throttle is increased, the low-speed 360° 1/8 Turn needle is pulled completely away from the needle seat, leaving it fully open. At that point, fuel Start 45° metering is entirely controlled by the high-speed needle. Again, using our water hose example, when the spray nozzle at the end of our garden hose is fully open, then the main water valve 3/4 Turn 1/4 Turn can be used to adjust how fast the water flows. 270° 90° The engine’s performance is directly linked to the fuel mixture. Richening the fuel mixture 1/2 Turn increases the amount of fuel in the air/fuel mixture ratio, and leaning the fuel mixture 180° decreases the amount of fuel in the air/fuel mixture ratio. • Slightly rich fuel mixtures deliver cooler • Slightly lean fuel mixtures deliver stronger, running and more lubrication but with more-efficient combustion and more power, slightly ­­­­less power. but with less lubrication. TRX ENGINES • 17 THE CARBURETOR

Tuning the engine means finding the Rich Lean perfect balance between the two; excellent power to meet your needs while maintaining good lubrication for long engine life. The optimal fuel mixture setting is rich to provide a safety margin against having a lean condition if some variable changes (such as the temperature from one day to the next). General fuel mixture settings are measured by the number of turns the needles are turned out from fully closed. The fuel mixture settings have been pre-set from the factory to typical break-in settings. Do not readjust your carburetor from the factory settings until after the engine is started and running and you have been able to observe the engine running to assess what minor adjustments may be required to compensate for fuel, temperature, and altitude. Adjustments are usually made in 1/8- or 1/16-turn increments.

The Idle Speed Adjustment The idle speed adjustment screw controls the closed position of the throttle slide. When the throttle servo is in its neutral position, the throttle slide should be stopped against the idle speed adjustment screw. Always use the idle speed adjustment screw to control engine idle. Do not use the throttle trim on the transmitter to adjust idle speed. The idle speed should be set as low as possible and still maintain reliable running.

18 • TRX ENGINES BREAKING IN YOUR TRX RACING ENGINE

BREAKING IN YOUR TRX RACING ENGINE Never run your model TRX Racing Engines use a ringless, aluminum-brass-chrome (ABC) piston/sleeve construction. indoors. Since model This type of engine design relies on a very precise running fit between the piston and sleeve engine exhaust fumes are for cylinder sealing. Engine break-in is necessary to allow the piston and sleeve to develop harmful, always run your an extremely precise fit and optimum cylinder sealing. Therefore, proper engine break-in is model outdoors, in a well- critical to achieving the fastest, most reliable engine performance. ventilated area.

1 Allow yourself about 1 to 1 /2 hours to complete the break-in procedure. The engine break- Your TRX Racing in period will take 5 tanks of fuel. The break-in time is not the time to impress your friends Engine doesn’t with your new engine. You must wait until the engine is fully broken in before attempting usually require priming. If sustained high-speed running. Patience and careful attention during break-in will reward you you do need to prime your with the best-performing TRX Racing Engine possible. engine, watch the fuel line carefully to avoid flooding During break-in, your engine may appear to malfunction with symptoms like stalling, your engine. See page 31 inconsistent performance, and fouled glow plugs. These are simply the normal “break-in for information on clearing pains” engines sometimes go through. They will disappear once your engine is fully broken in. a flooded engine. Many owners report not experiencing any of these symptoms with TRX Racing Engines. We recommend replacing the glow plug with a new one after the engine break-in procedure. Your carburetor is pre-set at the factory Engine Break-in Procedure to give the correct air-to- The focus during break-in is to vary and limit the engine speed. This will be accomplished by fuel ratio and idle speed accelerating and stopping at different rates for the first 5 tanks of fuel. As the engine begins for engine break-in. Do to break-in, the duration and intensity of the acceleration will gradually increase. Sustained not adjust the carburetor high-speed running is not permitted until the 6th tank of fuel. Perform the initial break-in on unless you observe a poor a large, flat, paved surface. Apply all throttle and braking actions gently. Abrupt acceleration running condition that or braking could cause the engine to stall unnecessarily. requires correction.

TRX ENGINES • 19 BREAKING IN YOUR TRX RACING ENGINE

See Safety Precautions Important points to remember during break-in: on page 4 for other • Special break-in fuels are not recommended. Use the same fuel you plan to use everyday. precautions. • If possible, avoid breaking-in the engine on extremely hot or cold days. • Pay careful attention to the fuel level. Do not allow the fuel tank to run completely empty. An extremely low fuel level causes the mixture to run too lean. This could result in a burned glow plug or extremely high engine temperatures. • Do not attempt to break in your TRX Racing Engine by idling it on a stand. This will produce poor results. • Keep extra Traxxas glow plugs handy. The break-in process can cause deposits to form on the plug, leading to plug failure. • Change or clean your air filter after break-in. • Follow the instructions exactly for each of the first 5 tanks of fuel. Starting Your TRX Racing Engine for the First Time Before you start your TRX Racing Engine for the first time, make sure you have read all instructions and precautions in this manual. Pay close attention to the tank-by-tank break-in instructions in the next section, and make sure you have read and understood them before you run your engine. Your engine must be at room temperature (70°F or 21° C) or above the first time you start it. If it’s cooler than room temperature outside, keep your TRX Racing Engine indoors until you’re ready to start it, then take it outside. 1. Turn on the radio system. 2. Make sure the throttle is in the idle position. 3. Pull the starter handle with quick, short, continuous pulls, and watch for fuel moving through the fuel line up to the carburetor. Watch closely! The fuel moves very fast. If the fuel doesn’t move through the line within 5 seconds, prime the engine by briefly (one or two seconds) covering the exhaust outlet until the fuel is just visible in the carburetor fuel line. Watch carefully! If the engine is primed too long, it will flood with fuel 20 • TRX ENGINES and stop turning. BREAKING IN YOUR TRX RACING ENGINE

5. Once fuel reaches the carburetor, the engine should quickly start and idle. As you gain 6. Proceed with the engine break-in. experience in the If your engine doesn’t start, refer to the TRX Racing Engine troubleshooting section at Traxxas. hobby, you may discover that many people have com/support. If your factory fuel mixture settings have been altered, refer to page 16. If you still differing opinions on what have problems, contact Traxxas Customer Support at 1-888-TRAXXAS or [email protected]. is the proper procedure to break-in a model engine. Tank 1 Only use the Traxxas 1. Drive the model with the body off. break-in procedure. Other 2. Driving procedure: Gently pull the throttle trigger to about 1/4 throttle over a 2-second break-in procedures count. Then, gently apply the brake to stop. Count the two seconds out while accelerating: could result in a weak, damaged, or otherwise poor one thousand one, one thousand two, and then stop. Operate the throttle trigger as performing engine. The smoothly as you can. Repeat this starting and stopping procedure until the first tank procedure outlined here of fuel is nearly empty. was extensively tested 3. Look for thick blue smoke exiting the exhaust outlet. If there is no smoke, richen the and proven to yield better high-speed needle 1/4-turn by turning the needle counterclockwise. performing engines than 4. When the fuel tank is nearly empty, shut off the engine by pinching the fuel line connected other “common” break-in to the carburetor (use the clamp if installed on your model). methods. Even if you have years of experience using 5. Let the engine cool for 15 minutes. model engines, please do Note: If at any point the engine cuts out or stalls during gentle acceleration, richen the high- not ignore this caution! speed needle 1/4-turn by turning the needle counterclockwise. Tank 2 1. From tank 2 forward, model should be driven with the body on. 2. Driving procedure: Gently pull the throttle trigger to about 1/2 throttle over a 2-second count. Then, gently apply the brake to stop. Count the two seconds out while accelerating: one thousand one, one thousand two, and then stop. Repeat this starting and stopping procedure until the second tank of fuel is nearly empty. 3. When the fuel tank is nearly empty, shut off the engine and let it cool for 15 minutes. TRX ENGINES • 21 BREAKING IN YOUR TRX RACING ENGINE

Tank 3 1. Driving procedure: Gently pull the throttle trigger to 1/2 throttle over a 3-second count. Then, gently apply the brake to stop. Count the three seconds out while accelerating: one thousand one, one thousand two, one thousand three, and then stop. Repeat this starting and stopping procedure until the third tank of fuel is nearly empty. 2. As the engine loosens, the idle speed may increase and cause the model to try to creep forward when stopped. Reduce the idle speed by turning the idle speed adjustment screw (see page 6) on the carburetor counterclockwise. 3. When the fuel tank is nearly empty, shut off the engine and refuel. From here on, you do not need to let the engine cool between tanks. Tank 4 1. Driving procedure: Gently pull the throttle trigger to full throttle over a 3-second count. Then, gently apply the brake to stop. Count the three seconds out while accelerating: one thousand one, one thousand two, one thousand three, and then stop. Repeat this starting and stopping procedure until the fourth tank of fuel is nearly empty. 2. Apply the throttle gradually! Your finger should not reach full throttle until the end of the three-second count. 3. Keep your driving smooth and consistent. 4. When the fuel tank is nearly empty, shut off the engine and refuel.

Tank 5 1. Driving procedure: Gently pull the throttle trigger to full throttle over a 3-second count, hold for 2 more seconds, and then gently apply the brake to stop. Count the five seconds out while accelerating. Repeat this starting and stopping procedure until the fifth tank of fuel is nearly empty. 2. The model should now be shifting into second gear. If it is not, try turning the high-speed needle clockwise 1/8-turn to lean the fuel mixture slightly and test for shifting. 3. When the fuel tank is nearly empty, shut off the engine and refuel. 22 • TRX ENGINES BREAKING IN YOUR TRX RACING ENGINE

Tank 6 High Altitude STOP! Clean your air filter before you proceed. Refer to the instructions on page 14. During Operation: the sixth tank of fuel, the engine can be tuned for general performance use. Proceed to the next If you live in a high section in this manual for instruction on tuning the engine. altitude region (5000 or more feet above sea level), Tank Throttle Time Cool Body Notes the lower air density may 1 1/4 2 Seconds 15 Minutes Off Apply throttle gradually. require you to lean your 2 1/2 2 Seconds 15 Minutes On Apply throttle gradually. high-speed fuel mixture 3 1/2 3 Seconds - On Reduce idle speed if necessary. slightly from the factory break-in settings. Try this 4 Full 3 Seconds - On Gradually accelerate over 3-second count. if you are experiencing 5 Full 5 Seconds - On Accelerate over 3-second count, difficult starting or hold for 2 seconds. extremely sluggish engine performance at Winter Break-in Tips high altitude. During the break-in process, the piston and sleeve wear into each other to form a precise fit. The engine needs to heat up to a temperature of at least 200°F to 215°F to allow the piston and sleeve to achieve this fit properly. A precise fit between these two components is critical for proper compression and optimum performance. If the engine runs too cold during break-in, the piston and sleeve will not expand to their appropriate sizes for break-in. This can lead to premature wear of these components. This wear may not become apparent until winter has passed and the engine is operated under warmer running conditions. • Warm the engine to approximately room temperature by removing all fuel and storing the vehicle inside at room temperature until just before starting the engine. An extremely cold engine can become difficult to start. • After the engine is running, it is important to keep the temperature of the engine to at least 200°F to 215°F during break-in. In weather below 45°F, your TRX Racing Engine will tend to run at lower temperatures between 160°F to 180°F (when tuned at proper break-in mixture settings). This is too cool for break-in. Do not lean the engine to increase engine temperature! This will also decrease lubrication and cause your piston/sleeve to wear prematurely. TRX ENGINES • 23 BREAKING IN YOUR TRX RACING ENGINE • Wrap the cooling head with a paper towel, clean rag, or sock to help keep the engine running at the recommended 200°F to 215°F break-in temp. If too much heat is contained, the engine may run too hot. Make sure that you monitor the engine’s temp closely for the first couple of tanks until you get the right amount of cover for the cooling head. This will, of course, depend on your current weather conditions. Adjusting the cover up and down, exposing more or fewer cooling fins, is a convenient way to regulate engine temps. • For owners that do not have access to a temperature probe, a drop of water on the cooling head (around the glow plug area) should slowly sizzle for approximately 6 to 8 seconds when the engine temp is 200°F to 210°F. If the water sizzles for only a few seconds, then it is likely that the engine temp is over 220°F and needs to cool down. If the water takes a long time or does not evaporate at all, then the engine is too cool. • We do not recommend that you operate your engine below 35°F. If you insist on running your vehicle below 35°F, be aware that nitro engines may be very difficult to start and tune at those extremely cold temperatures. Also, at temperatures below freezing, nitro fuel can actually begin to gel up, which can be harmful to the engine. • Follow the remaining break-in procedures as outlined in this owner’s manual. This, along with the steps listed above, will ensure a good break-in for your new nitro engine and provide many hours of enjoyment.

24 • TRX ENGINES TUNING YOUR TRX RACING ENGINE

TUNING YOUR TRX RACING ENGINE When tuning for The engine’s performance depends on the fuel mixture. Turn the mixture needles clockwise performance, watch to lean the fuel mixture and counterclockwise to richen it. Leaning the fuel mixture will closely to notice when there increase engine power up to the engine’s mechanical limits. Never run the engine too lean is no longer any increase in (not enough fuel flow). Never lean the engine until it begins to cut-out or stall. Leaning the speed or power when the engine beyond the safe allowable limits will result in poor performance and almost certain high-speed mixture is lean. engine damage. Indications of an overly lean mixture include: If you lean the high-speed mixture to the point that the • Cutting out or sudden loss of power during acceleration. engine cuts-out, hesitates, • Overheating (temperature beyond 270°F at the glow plug) or stalls, you are well into • Little or no blue smoke coming from the exhaust. the danger zone and engine If any of these conditions are present, stop immediately damage is likely. Richen the and richen the high-speed mixture 1/4-turn. The engine high-speed needle 1/4-turn will probably be slightly rich at that setting and and retune. you can then retune for performance. Always tune for performance by starting rich and moving leaner toward the ideal setting. Never try to tune Higher nitro requires from the lean side. There should always be a a richer fuel mixture. light stream of blue smoke coming from the When running 33% fuel, exhaust. Before you begin tuning, the engine richen your high-speed should be warmed up to its normal operating needle 3/4-turn if previously temperature and running slightly rich. All final running 20% nitro and then re-tune the engine for tuning adjustments must be made to the engine at maximum performance. its normal operating temperature. You can tell the engine is running rich by noting any of the following: • Sluggish acceleration, with blue smoke coming from the exhaust • Unburned fuel spraying from the exhaust tip • Leaning the high-speed fuel mixture increases performance TRX ENGINES • 25 TUNING YOUR TRX RACING ENGINE High-Speed Fuel Mixture Adjustment For your convenience, With the engine warm and running at a rich setting, gradually lean the high-speed fuel mixture the low-speed needle has a positive stop that in 1/16-turn increments. Make several high-speed passes after each adjustment to clear out prevents it from being over- the engine and note any change in performance. TRX Racing Engines are extremely powerful. tightened and damaging Remember to apply the throttle gradually to prevent wheelies or loss of control. Continue this the needle and seat. This procedure until there is no longer any performance improvement. If any one of the following also provides an easy way to conditions occurs, the fuel mixture is already past the maximum safe lean setting: gauge how many turns out 1. There is no longer any performance improvement. from closed the low-speed 2. The engine begins to cut out at high speed (Danger!). needle adjustment is set to. 3. There is a sudden loss of power during acceleration (Danger!). 4. The engine begins to overheat. Symptoms of overheating include: • Fluctuating idle speed • Temperature measurement above 270°F When adjusting • Hesitation or stalling during acceleration at the glow plug (A temperature reading the low-speed • Steam or smoke coming from the engine above 270°F alone does not necessarily fuel mixture, it is very (not exhaust) indicate overheating. Look for other important to make several • Popping or clattering sound when symptoms of overheating combined with high-speed runs with decelerating (detonation) temperature for a more accurate warning.) your model between adjustments to clear out If any of the above conditions occur, richen the fuel mixture to the optimum setting by any excess fuel. Perform richening the high-speed needle at least 1/8-turn counterclockwise and retest. This setting the pinch test immediately will extend engine component life. after. If the engine is Low-Speed Fuel Mixture Adjustment allowed to idle for a long The low-speed mixture is always set after the high-speed needle is correctly adjusted. period of time, it could Set the low-speed mixture using the following pinch test. “load up” with fuel and 1. Once the engine is warm, do several high-speed runs to confirm that the high-speed needle give you an inaccurate is set correctly. measurement from your 2. Bring the vehicle in and pinch closed the fuel line going into the carburetor. The engine pinch test. should run for 2-3 seconds, speed up, and then die.

26 • TRX ENGINES TUNING YOUR TRX RACING ENGINE 3. If the engine runs longer than 3 seconds, then lean the Fine-Tuning the Carburetor low-speed needle 1/16-turn, make several more high- After fine-tuning your TRX Racing Engine at the end of the speed runs, and retest. break-in procedure, no major adjustments to the fuel mixture 4. If the engine dies immediately without speeding up, then are usually necessary. Make note of the temperature, humidity, richen the low-speed needle 1/8-turn, make several more and barometric pressure at the time you finished fine tuning high-speed runs, and retest. your carburetor. Current weather conditions can be found online When the low-speed needle is set correctly, the engine’s throttle from national websites, local TV news websites, and television. response should be very quick. This information will be considered your baseline setting. You may need to adjust your carburetor needles to compensate for Idle Speed Adjustment changes in temperature and barometric pressure (air density) Once the high- and low-speed mixtures have been set, reduce from day to day. Generally, you’ll need to richen the fuel mixture the idle speed to the minimum reliable idle speed. Remember, when the weather is colder than your baseline temperature and this adjustment should be made while the engine is running at the air density is higher. Lean the fuel mixture when weather normal operating temperature. is warmer than your baseline temperature and the air density 1. Make sure that the throttle slide is stopped against the is lower. The chart below provides general guidelines on how idle speed adjustment screw by releasing the throttle weather conditions affect air density when they move higher or trigger to neutral or adjusting the throttle trim on the lower than your baseline setting (see page 16 for detailed info transmitter (depending on model) so that the brakes are on how air density affects mixture settings). applied. Note: Remove the air filter to gain access to the idle speed adjustment screw, then the air adjust (correct) the if necessary. IF THE... IS... density is... fuel mixture to be... 2. Turn the screw counterclockwise Humidity Lower Slightly more dense Slightly richer to reduce the idle speed or Higher Slightly less dense Slightly leaner clockwise to increase it. The idle Pressure (barometer) Lower Less dense Leaner speed should be set as low as Higher More dense Richer possible while still maintaining Temperature Lower More dense Richer reliable running characteristics. Higher Less dense Leaner 3. If equipped, reset the throttle Altitude Lower More dense Richer trim on the transmitter to its Higher Less dense Leaner original position. Nitro % Lower Leaner Higher Richer TRX ENGINES • 27 TUNING YOUR TRX RACING ENGINE

Tuning the Engine by Temperature the engine temperature. Generally, try to keep your engine from The following procedures require exceeding 270°F when measured at the glow plug. If necessary, an optional infrared temperature increase airflow to the engine by cutting out the rear of the body, probe or on-board temperature windshield, and front valance. In some situations, the engine gauge (Traxxas on-board digital may perform very well with no stalling, lagging, or hesitation at temperature gauge, part #4091). Engine temperature can be used temperatures above 270°F, particularly in very hot climates. If as an effective tuning aid when you understand the relationship richening the fuel mixture to bring the temperature down to 270°F between engine temperature and ambient temperature. The results in poor, sluggish performance (engine never cleans out), engine operating temperature, when tuned for maximum then return the engine back to a satisfactory state of tune based performance, will vary according to atmospheric conditions, on how it sounds and performs (always with a visible stream of engine load, gauge accuracy, and many other factors. The blue smoke coming from the exhaust). If engine temperature is atmospheric condition that has the most influence on engine exceeding 270°F with proper cooling and no signs of abnormal temperature is air temperature. Expect the engine temperature running, then avoid running the engine at its maximum lean to vary almost in direct proportion to air temperature. Assuming setting. Watch closely for any signs of overheating. Richen the fuel you tuned the engine for the same maximum performance each mixture slightly to provide a safety margin of additional cooling day, the engine will run about 20° hotter when it’s 90°F outside lubrication. Symptoms of overheating include: than it would in 70°F weather. For this reason, we cannot give you • Steam or smoke coming from the engine (not exhaust) a definitive temperature range that indicates the best possible • Hesitation or stalling during acceleration engine tuning. • Popping or clattering sound when decelerating (detonation) The temperature gauge can aid you in tuning by giving you a • Fluctuating idle speed relative indication of how your adjustments are affecting the There is NO optimal temperature that can be used as a engine and to help prevent you from reaching excessive engine target to deliver the best engine tuning. Do not rely on a temperatures. For example, as you lean the fuel mixture, the temp gauge alone to tune your engine. Tune the engine by engine performance will increase along with the temperature. paying very close attention to how it responds to changes If you continue to lean the fuel mixture and the temperature in fuel mixture (more smoke/less smoke, fast/sluggish, increases but the engine performance does not change, then reliable/stalling, smooth sound/ muffled sound, etc). Once you have exceeded the maximum safe lean setting. Make note of the engine is tuned, then observe the temperature. TRX ENGINES • 28 TROUBLESHOOTING YOUR TRX RACING ENGINE TROUBLESHOOTING YOUR TRX RACING ENGINE The following section addresses some very basic engine and radio questions you may have about your TRX Racing Engine. Most questions arise from simple user errors or minor adjustments that are easy to correct. If you can’t find a solution for your TRX Racing Engine here, visit our web site at Traxxas.com and click on the Customer Support menu. There you will find a much more extensive and detailed online troubleshooting area. In addition, you may call Traxxas Customer Service at 1-888-TRAXXAS (outside the U.S., call +1-972-265-8000). Engine spins but will not start: • If you’re using a glow plug igniter, make sure it’s fully charged and connecting properly to the glow plug. If the igniter is fully charged, then replace the glow plug. It is normal for glow plugs to require periodic replacement. Only use Traxxas heavy-duty long glow plugs. • Check to make sure the fuel is getting to the carburetor. Remove the fuel line where it connects to the carburetor to see if there is fuel in it. If not, you may need to prime the engine. Reconnect the fuel line and then refer to page 20 for instructions on priming the engine. • Check your fuel mixture settings. It may be necessary to adjust the fuel mixture if the outside temperature or barometric pressure has changed significantly since the last time the engine was run (see Fine-Tuning the Carburetor on page 27). Turn the high-speed needle out (rich/ counterclockwise) 1/4-turn, hold the throttle trigger at about 1/2 throttle, and try again to start the engine. Once started, retune the engine for performance (see page 25). • The engine could be worn. If the fit between the piston and sleeve is loose, compression is reduced and the engine will be difficult to start when it is warm, and may tend to stall when running and when the throttle is closed suddenly to idle. Engine life depends on many factors, including fuel type, air filter maintenance, needle settings, and how the engine was used. For example, if the engine was allowed to ingest dirt from lack of air filter maintenance or running through water, then the internal engine components could wear out extremely fast. • Glow plug may have failed. If using an EZ-Start, check to see if the glow plug light is on when starting. If not, replace the glow plug. If using a glow ignitor, remove and check the glow plug.

TRX ENGINES • 29 TROUBLESHOOTING YOUR TRX RACING ENGINE

Engine performance sluggish: • Engine performance depends mostly on the fuel mixture settings and how they compensate for the current atmospheric conditions. Before you suspect other failures with the engine, richen the high-speed needle at least 1/4-turn and then retune the engine for performance (see page 25). • Try a new Traxxas glow plug. Sometimes a glow plug will work well enough to start the engine but not be able to deliver the engine’s full performance potential. • If the fuel mixture seems to be set correctly, make sure the fuel is fresh. If the fuel is old, or was left uncapped for a long period, then some of the important fuel components could have evaporated. Try new, fresh, Traxxas Top Fuel. • Check to make sure there is no binding in the driveline that would cause excessive loads on the engine. Engine will not spin (pull start or electric starter will not turn the engine): • The engine could be flooded. If too much fuel accumulates in the combustion chamber at start up, the engine will hydraulically lock. Follow the procedure on page 31 for clearing a flooded engine. • Check for binding at the engine flywheel. If you are not able to turn the engine by hand, the engine could be flooded, there could be binding in the clutch system, or there could be internal engine damage. See page 31-32 for info on clearing a flooded engine and releasing a stuck piston. (Note: It is normal for the engine to be extremely tight and hard to turn when the piston reaches the top of the compression stroke.) • Piston stuck at top dead center, see page 32 for info on unsticking the piston. Engine extremely sluggish, hard to start, and will not idle during tank 1 of the break-in: • It is possible that the factory adjusted break-in settings on your carburetor are too rich for your geographic location, atmospheric conditions, or fuel brand. Extremes in temperature, humidity, barometric pressure, and altitude can’t always be accounted for with a single high-speed needle setting. The symptoms described above can occur when the air density is very low, such as in high

30 • TRX ENGINES TROUBLESHOOTING YOUR TRX RACING ENGINE

mountainous elevations and extremely cold temperatures. Under these conditions, lean the fuel mixture slightly, 1/8-turn, and see if there is any improvement in starting and idling. Lean the fuel mixture only until the engine will run and idle reliably, and then proceed with the break-in. • The contents of different brands of fuel (other than Traxxas Top Fuel) in combination with extreme atmospheric conditions can also make the factory preset break-in settings too rich and cause the symptoms described above. Again, try leaning the fuel mixture slightly, 1/8-turn, to see if there is any improvement in starting and idling. Clearing a Flooded Engine: If the engine is primed for too long during startup, it can become flooded with fuel. When the engine is flooded it will no longer turn due to excess fuel in the combustion chamber, preventing upward movement of the piston. Use the following procedure to clear a flooded engine: 1. Remove the glow plug and gasket with the glow plug wrench supplied with your model. A 5/16” (8mm) nut driver will also work. 2. Turn the model upside down. 3. Pull the starter handle several times to clear the engine of excess fuel. 4. Turn the model over and reinstall the glow plug and gasket. 5. Do not prime the engine. Apply 1/2 throttle and pull the starter. The engine should start immediately.

TRX ENGINES • 31 TROUBLESHOOTING YOUR TRX RACING ENGINE

Piston stuck at “top dead center” (TDC) “Top dead center” is the position where the piston is at the very top of the tapered sleeve. Occasionally an engine can get “stuck” at this position. This is most likely to happen on new engines during break-in, but can also happen at other times. If the engine is stuck at TDC, use the following procedure to release the piston from the sleeve: 1. Remove the glow plug using a 5/16" (8mm) nut driver and verify that the piston is at the top of its stroke. 2. Locate the flywheel at the front of the engine; it looks like a silver 50-cent piece with serrated edges. Part of the flywheel is obscured Top Dead Center beneath the carburetor, but part of it is accessible from the top side. This is the part of the flywheel where the procedure is performed. 3. Use a flat-blade screwdriver to rotate the flywheel. Place the blade of the driver into one of the grooves of the flywheel and push down, turning the flywheel counterclockwise when viewed from the front. You should see the flywheel turn and the piston should become unstuck from the sleeve. [T-Maxx and Revo: Place the blade of the driver through the opening of the chassis beneath the flywheel. Place the edge of the blade into one of the grooves of the flywheel and rotate counterclockwise (when viewed from the front), using the chassis for leverage.] 4. Put two or three drops of light machine oil into the glow plug hole to lubricate the piston and sleeve. Do not use too much oil. It will hydro-lock the engine. Verify the starter will spin the engine with the glow plug out. 5. Rotate the flywheel so the piston is at bottom dead center and replace the glow plug with gasket. 6. You should now be able to start the engine. Bottom Dead Center 32 • TRX ENGINES MAINTAINING AND STORING YOUR TRX RACING ENGINE

MAINTAINING AND STORING YOUR TRX RACING ENGINE If the engine is Your TRX Racing Engine requires timely maintenance in order to stay in top running condition. worn or damaged Neglecting maintenance could allow dirt, deposits, and moisture to build up inside the engine, enough to require replacing leading to internal engine failure. Follow proper maintenance and storage procedures to avoid the piston, sleeve, or damage to your engine. The following procedures should be taken very seriously. connecting rod, consider exchanging your old engine After each hour of running: for a brand new engine • Clean and re-oil the air filter. The instructions for this procedure are on page 14.We cannot stress under the terms of the enough the value of cleaning your air filter at the scheduled intervals. The cleanliness and Traxxas Power Up Program. condition of your air filter directly influences the running life span of your engine. Do not skip It could save you time and air filter maintenance! effort. Details are in your documentation package or • Clean the outside of the engine of accumulated dirt, oil, and grime. Accumulated grime will at Traxxas.com/powerup. decrease the engine’s ability to cool itself. After each running session: Don’t put the fuel • Perform after-run maintenance on the engine. This clears the engine of destructive moisture and from your tank back other corrosive deposits. This is extremely important for the life of the engine. See page 34 for into your fuel jug. Dispose of it properly, following city after-run maintenance procedures. or county regulations. • Inspect the vehicle for obvious damage or wear. Look for: 1. Loose or missing screws 2. Cracked, bent, or damaged parts Always wear eye 3. Cut or loose wiring protection when using compressed air or spray 4. Cut or kinked fuel lines cleaners and lubricants. 5. Signs of fuel leakage • Inspect the gears for wear, broken teeth, or debris lodged between the teeth.

TRX ENGINES • 33 MAINTAINING AND STORING YOUR TRX RACING ENGINE After-run Procedure Denatured alcohol (available from You must perform after-run maintenance on your Traxxas engine whenever the model will be home centers and paint stored for longer than a few hours. Taking the time to prepare your engine for storage will reward supply stores) in a spray you with longer engine life, easier starting, and better performance. bottle is an extremely effective cleaner. Be sure When a nitro engine is shut off, some excess unburned fuel remains in the engine. The methanol in to wear safety glasses and model engine fuel is hygroscopic, which means it easily attracts and absorbs moisture. This moisture gloves when working with can cause rust and corrosion on the steel engine parts (crankshaft, bearings, wrist pin, and starter denatured alcohol. Follow all precautions on the product shaft) if the fuel is not removed from the engine. There are after-run oil products available from your ™ labeling. hobby dealer or you can use WD-40 , a common household lubricant. To ensure your TRX Racing Engine is protected from internal corrosion, use the following procedure: 1. Shut off the engine by pinching the fuel line closed. This allows most of the excess fuel to be consumed by the engine. Be sure the throttle is in the idle position. You may have to pinch the fuel line closed for several seconds before the engine stops. 2. Completely empty the fuel tank. Use your fuel-dispensing bottle to suck out the old fuel. Do not mix the old fuel with your fresh fuel supply. If you leave fuel in the tank, transporting or handling your model may cause fuel to run into the engine. 3. With the fuel tank empty and the throttle at the idle position, try to start the engine. The engine will most likely start and run for a few seconds as it uses up any fuel remaining in the engine and fuel lines. 4. Once the engine stops, clean the outside of the engine with compressed air or spray motor cleaner. Once the engine is clean and dry, remove the (blue) glow plug power wire, glow plug, and air filter. 5. Open the throttle fully and spray a one-second burst of WD‑40™ into the carburetor and into the glow plug hole (CAUTION! Wear safety glasses to prevent spray from getting into your eyes). 6. Place a rag or paper towel over the engine to catch any WD‑40™ that may come out of the carburetor or glow plug hole. 34 • TRX ENGINES MAINTAINING AND STORING YOUR TRX RACING ENGINE

Do not store your 7. Crank the engine with the EZ-Start™ (or pull the starter handle) continuously for model indoors with about 10 seconds. fuel remaining in the tank 8. Remove the rag or paper towel and repeat steps 5–7 two more times. or the engine. 9. Clean and re-oil the air filter so it will be ready for use next time. See page 14 for air filter maintenance instructions. TRX engines are 10. Replace the glow plug and reinstall the air filter. designed to be easily rebuilt. Critical Other periodic maintenance: engine components such • Piston/sleeve: The life of the piston and sleeve will vary greatly with how the engine as the crankcase, crankshaft, was used and maintained. The piston and sleeve should be replaced when they no and engine bearings are made to extremely high longer seal effectively (loss of compression). Symptoms include the engine being quality standards and should difficult to start when warm, stalling when warm, and stalling when throttle is suddenly under normal circumstances closed to idle. Replace the wrist pin and G-clip whenever the piston and sleeve are outlast multiple sets of replaced. Follow the instructions for the proper break-in procedure of a new TRX Racing pistons, sleeves, connecting rods, and wrist pins Engine whenever the piston and sleeve are replaced. (reciprocating assemblies). • Connecting rod: The connecting rod should be replaced when the piston and sleeve It could be more economical for you to continue to use are replaced or after three gallons of fuel, whichever comes first. Also replace the piston your good bearings and wrist pin and G-clip whenever the connecting rod is replaced. As with other internal crankshafts, and simply engine components, the connecting rod’s life depends on the engine’s usage and the replace the reciprocating quality and frequency of the engine’s maintenance. assembly as needed. Engine assembly is not difficult and replacing the reciprocating assembly does not require any special tools or skills.

TRX ENGINES • 35 REBUILDING YOUR TRX RACING ENGINE

101 These instructions are for the rebuilding 201 2. Remove the 5.0mm E-clip from the of the TRX Racing Engine once the engine crankshaft (Nitro 4-Tec owners will need has been removed from the chassis. (These to remove the 3x10CS screw) and slide the instructions were performed on a TRX 3.3 5x8x0.5PTW with the clutch bell off engine equipped with the EZ-Start electric of the crankshaft (Nitro 4-Tec owners will starting system and Revo exhaust system. need to slide two 5x8x0.5PTW off the Other TRX Racing Engines and engines pilot shaft.) CAUTION: It’s important to equipped with pull starters or backplates use eye protection when removing the [without starter] are similar.) 102 202 E-clip from the shaft to prevent the clip It is very important to clean the exterior from causing an injury. Pull the clutch of the engine and EZ-Start system shoes off of the flywheel pins. thoroughly before disassembly. These instructions show you how to replace the Remove the flywheel nut from the entire internal reciprocating assembly. crankshaft using an 8mm socket (202) The following instructions are for and disconnect the flywheel from the engines equipped with IPS crankshafts crankshaft by lightly tapping the back 103 using Traxxas clutch components. For 203 of the flywheel with a rubber or Multi-shaft™ crankshafts in non-Traxxas plastic mallet. applications, follow the manufacturer’s directions for clutch installation/removal. Place a small flat-blade screwdriver into the slot of the split cone washer and twist 1. Remove the exhaust pipe and header slightly to loosen the split cone from from the engine by removing the two 3x15CS screws (102 & 103). the crankshaft (203). Slide the split cone washer off of the crankshaft. The engine 104 If your engine is equipped with a 204 is now ready to be rebuilt (204). starterless backplate, proceed to step 2. Remove the three 3x12BCS screws that secure the EZ-Start (or pull start) assembly to the engine and separate the drive unit from the engine (104). Be sure to remove the 6x8x0.5 PTFE-coated washer that is installed on the starter shaft between the one-way bearing and the engine. TRX ENGINES • 36 REBUILDING YOUR TRX RACING ENGINE

301 3. Remove the glow plug from the 403 Rotate the crank to where the cooling head and discard the plug. connecting rod and piston are The glow plug should be replaced located at TDC (403). with a new one anytime the engine is rebuilt. Gently pull on the bottom of the connecting rod with needle- Remove the four 3x6CS (3x6BCS on nose pliers, sliding the rod off of the engines equipped with non-starter crank pin (403). Be careful not to 302 backplate) screws from the backplate of 404 damage the connecting rod if it is the engine and pull the backplate from being reused. the crankcase (301). The rod and piston assembly will exit Remove the head protector (requires the top of the crankcase (404). removal of five 3x8CCS on the TRX 3.3). Remove the cooling head from 5. Push the end of the pilot the engine case by removing the five shaft through the crankcase. The 3x12CS head bolts (302). Be careful crankshaft should exit the rear of 401 501 not to lose or damage the copper the crankcase (501). Loosen the 3.0NL head gasket. If the head gasket is just below the base of the carburetor damaged, replace it with a new one. (502). Slide the carburetor up and out of the crankcase (503). Now the 4. Locate the bottom of the sleeve crankcase is ready to be flushed through the rear opening of the clean and inspected. crankcase. Press the bottom of the sleeve upward with a plastic or 402 wooden stick (401), this is to prevent 502 503 internal damage to the crankcase. The sleeve should slide up and out of the crankcase (402).

TRX ENGINES • 37 REBUILDING YOUR TRX RACING ENGINE

601 6. Flush the crankcase and bearings 801 Important: Do not reuse a damaged out with out with denatured alcohol or or worn crankshaft. This will dramatically electric motor spray. Dry the crankcase shorten the life of your rebuilt engine. with compressed air (601). CAUTION: If there are damaged or worn parts beyond Do not let the compressed air spin the piston, sleeve, and connecting rod, it the bearings, and always use eye may be best to take advantage of the Traxxas protection when using compressed air. Engine Replacement Program (ERP). Inspect the crankcase and bearings for 8. Use after-run oil to lubricate the bearing damage or missing parts. Make sure surfaces of the crankshaft before assembling 602 that the bearing cages are not broken 802 it into the crankcase. Slide the crankshaft and check for corrosion inside of the back through the crank bearings until it crankcase. The bearings should feel stops. Inspect the carburetor O-rings for smooth and have little play. Make sure damage and the rubber throttle arm boot for the bearings spin freely and that there tears (801 & 802). are no particles or grit in them. Replace Unscrew the high-speed needle all the way the bearings if there are any signs of out of the needle housing (803) and flush damage. Inspect the exhaust O-ring out the high-speed needle housing and the gasket and the backplate O-ring gasket 701 803 carburetor body with denatured alcohol or for tears (602). Replace these O-rings electric motor spray. Use compressed air to if needed. dry the components. Remember: Always 7. Apply a few drops of machine oil or wear safety glasses when using compressed after-run oil to the bearings. Inspect the air to prevent injury. Reinstall the high-speed needle into the needle housing and return crankshaft for corrosion and also check the mixture setting back to the factory for scratches or score marks around the recommended break-in setting (4-turns out intake port of the crankshaft (see arrow). from fully closed). Check the crank pin for wear (701). The connecting rod should fit and rotate 804 Carefully insert the carburetor into smoothly on the crank with no play the crankcase until fully seated. While between the rod and the crank pin. If pressing the carburetor firmly into the there is play between a NEW connecting crankcase, tighten the pinch bolt (804). rod and the crank pin then the crank pin This process ensures that the upper is worn and the crankshaft will need to O-ring forms a good seal between the be replaced. carburetor and the crankcase. TRX ENGINES • 38 REBUILDING YOUR TRX RACING ENGINE

901 9. Apply a drop of after-run oil in the 1002 10. Lube the outside of the piston Skirt piston’s wrist pin bore, before installing with after-run oil and make sure the Relief the wrist pin. Locate the oil hole (refer to crank is at BDC, then slowly lower the pic 901) in the connecting rod and the sleeve until It is just above the piston. skirt relief side of the new piston. Oil Rotate the crank slowly to bring the Hole Insert the connecting rod into the piston piston into the sleeve. If there is any with the piston skirt relief and the oil resistance, stop! Repeat until the hole on the same side (901). Line up the piston moves smoothly into the sleeve. 902 Skirt Relief wrist pin bore in the rod with the wrist 1003 Bring the piston close to TDC, then Oil pin bore in the piston and slide the wrist push the sleeve in fully. Important: The Hole pin through the larger opening in the slot (in the lip) at the back of the sleeve piston. Note that the closed end of the must key into the pin at the back of wrist pin should be inserted first into the the crankcase opening (1001). Do not opening. The orientation of the wrist pin install the cooling head until these two helps keep the wrist pin cool. items are keyed into each other. Install the wrist pin clip into the groove 903 Place the stock copper head gasket of the piston’s wrist pin bore (902). This onto the sleeve and fit the cooling head into the sleeve. Note that will retain the wrist pin inside of the there are two slots notched through the cooling fins on each side of piston. CAUTION: Do not allow the the cylinder head. These slots are for access to the engine mounting pliers to scratch the piston, and make screws. The five head bolts should line up with the five holes on top of sure that the clip expands into the the engine case and the access slots on the cooling head should line groove. up with the slots manufactured into the crankcase (see picture 1002 for Lower the piston and connecting rod orientation). Be careful not to damage the copper head gasket. 1001 assembly into the top of the engine While pressing the head squarely onto the sleeve, thread the head bolts case with the oil hole of the connecting into the engine case just until they stop. Do not tighten down these bolts rod facing toward the crankshaft. Apply individually. It is very important to attain even pressure around the cooling a drop of oil onto the crank pin before head. Slowly tighten each screw, just a little at a time, in a crossing pattern installing the connecting rod onto the (see picture 1003) until each bolt becomes snug. Tighten each bolt in the crank pin. Slide the connecting rod over same pattern to 9-11in•lbs. of torque. the crank pin and rotate the crank pin to the bottom center of the crankcase (903). TRX ENGINES • 39 REBUILDING YOUR TRX RACING ENGINE

1101 11. Inspect the backplate bushing and 1203 and onto the split cone washer. starter shaft for wear and clean them The split cone washer should fit inside with denatured alcohol. Fasten the of the tapered hole in the flywheel. backplate with the starter shaft to the Thread the flywheel nut all the way up crankcase. Important: The reliefs that to the flywheel and tighten the flywheel are manufactured into the backplate to 55-65 in•lbs. of torque against the must line up to match the ports inside flywheel (1202). of the engine case (see picture 1101 13. Slide the clutch shoes onto the 1102 for orientation). 1301 flywheel. Key the flywheel pins into the Key the starter shaft to the crank pin holes of the clutch shoes (See picture by slowly rotating the starter shaft 1301 for orientation of the clutch shoes). as pressure is applied towards the Tip: By reversing the direction of the crankshaft. Once the starter shaft clutch shoes, the clutch shoes will is keyed into the crank pin, join the provide a little firmer bite against the backplate to the engine case and interior wall of the clutch bell. This is secure the assembly with the four useful on higher bite surfaces that offer 1201 3x6CS screws (1102). (On non-starter 1401 a higher level of traction. models, simply align the reliefs in the backplate and fasten it to the 14. Clean and lube both clutch bell crankcase with (4) 3x6BCS screws). bearings and install a ball bearing into each side the clutch bell and slide the Install a new glow plug (Traxxas #3232 clutch bell over the pilot shaft, followed is recommended for your TRX Racing by the 5x8x0.5PTW (1401). Engine) into the cooling head. The 1202 engine is now rebuilt and ready for the With safety glasses on, fasten the 5.0 installation of the clutch assembly and E-clip around the pilot shaft to retain the the EZ-Start system (if so equipped). clutch assembly. Note: The Nitro 4-Tec will need two 5x8x0.5PTW placed onto 12. Slide the split cone washer over the the pilot shaft before the installation of pilot shaft with the larger end of the the clutch bell, then secure the assembly taper toward the engine case (1201). with the 3x10CS screw. Slide the flywheel over the pilot shaft TRX ENGINES • 40 REBUILDING YOUR TRX RACING ENGINE

1501 Shaft 15. Clean the roller clutch with denatured alcohol or electric PTFE-coated Roller Washer Clutch motor spray, and lube the roller clutch with Mobil 1® 5W30 oil. Slide the PTFE-coated washer and roller clutch onto the starter shaft as shown (1501). Note: The roller clutch is to be installed onto the starter 1502 shaft so that the clutch engages the starter shaft clockwise and rotates freely counterclockwise. The engraved text on the roller clutch faces the engine backplate for correct rotation. Slide the EZ-Start system or pull start onto the starter shaft that exits the backplate of the engine. Line up the drive with the roller clutch. Fasten the EZ-Start gear case to the backplate with three 3x12BCS screws (1502), or the pull 1601 starter with four 3x12BCS. 16. Inspect the exhaust O-ring and replace it if it is damaged. Fasten the exhaust header and pipe assembly back onto the rear of the engine case with the two 3x15CS screws (1601). 17. Reinstall the head protector (requires five 3x8CCS on the TRX 3.3). 1602 The engine, clutch, exhaust system, and starter assembly are now ready for installation into the chassis (1602). Follow the instructions for the proper break-in procedure of a new TRX Racing Engine (page 19).

TRX ENGINES • 41 INDEX

.20; 7 Crankshaft; 6, 7 ABC; 7, 19 Cylinder head; 8 After-run Procedure; 34, 35 head protector; 6 Air Filter; 5, 6, 7, 8, 14 PowerTune™ head; 6 filter foam; 8 Dyno; 8 Air Intake; 6 EZ-Start; 8 Backplate; 6 Fit; 8 Break-in; 7, 14, 19, 21, 22, 23 Flame-out; 8 Tank 1; 21 Flywheel; 6 Tank 2; 21 Fuel; 8 Tank 3; 22 intake; 6 Tank 4; 22 tubing; 8 Tank 5; 22 Fuel Mixture; 8 Tank 6; 23 high-speed mixture; See High-Speed Fuel Carburetor; 6, 7 Mixture Adjustment carb; 7 lean; 9, 17, 18 factory settings; 16 leaning; 9 fine tuning; 27 low-speed mixture; See Low-Speed Fuel slide; 10 Mixture Adjustment Clean-out; 7 rich; 10, 18 Clutch Bell; 6 Glow plug; 8 Combustion chamber; 7 driver; 8 Connecting rod; 7 Header; 8 Cooling fins; 8 High-Speed Fuel Mixture Adjustment; 26 Crankcase; 6, 7 high-speed needle; 6, 9

42 • TRX ENGINES INDEX Idle Speed; 9, 18, 27 idle speed adjustment screw; 6, 9 Low-Speed Fuel Mixture Adjustment; 26 low-speed needle; 6, 9 Maintaining and Storing; 33 Needle valve; 9 Nitro; 9 O-ring; 9 Piston; 9 Port; 9 Priming; 10 Pull Starter; 6 Safety; 4 Sleeve; 10 Stall; 10 Starting; 20 Throttle Arm; 6 Top dead center (TDC); 10, 30, 32 Troubleshooting; 30 clearing a flood; 31 Tuned pipe; 10 Tuning; 25 by temperature; 28 fine-tuning; 27 Wear-in; 10 WOT; 10

TRX ENGINES • 43 1100 KLEIN ROAD, PLANO, TEXAS 75074 1-888-TRAXXAS 130103 KC0509-R01