Xentric Theoretical Automotive Design

Xentric automotive technologies

Boosting horsepower & R.P.M. (Mopeds 50-80cc all makes) (4-stroke)

When boosting horsepower it is essential for one to know the principal subsystems, they’re function and how they will be affected by a sudden increase in efficiency and torque. Without any attention given to these principals, premature wear, excessive vibration and possible complete engine seizure can easily put an end to your ambitious project. This document will cover key components, give a brief detail of their functions and ultimately show how to improve their efficiency resulting in an increase in horsepower.

Intake & air filtration systems Carburetion & gas channel systems Displacement & piston Crankshaft & connecting-rod assembles Camshaft Flywheel & electronics Bearings Clutch Gearbox Sprockets Exhaust Lubrication systems Spark plugs Proper maintenance

Much of what is talked about is generalized to fit all situations and may not apply to certain models due to differing design and manufacture. This should also be taken as a guide to higher performance, not an instruction manual. (Reader’s discretion is advised!) Intake & air filtration systems The purpose of the intake system is to supply a source of clean air to any given form of carburation subsystem. It is normally comprised of a filter and an airbox or filter sheath. The air filter cleans the air before it is sent through the carburetor and later to the combustion chamber. Filtration prevents dirt and grit from entering the delicate carb and combustion chamber, which results in gum-up and premature wear. It also however constricts airflow (venturi theory) causing a choking effect slowing engine performance and richening the fuel mixture. This may be good on a cold engine, but no for a hot one and must be dealt with if high performance is an issue. One way of dealing with such problems is by replacing the stock filter with a powerfilter. These filters are often made of very fine porous material that offers very little air constriction under all kinds of conditions/situations. Installing such a fixture may also result in the need to tune the carb to make up for the sudden rush of air. A rich carburation mixture is advisable, solving the new problem of too much air. Another way of dealing with air constriction is by running a multi filter system via manifold instead of airbox. Doing so ensures enough airflow at top end performance to eliminate the effects of constriction at the airbox, allowing for high R.P.M. and quick engine response. Once again rich carburation is advisable. Turbo charging is a different matter. It is possible to run a blower off a jackshaft leading to the flywheel and turbo-charge your intake system but it is advisable you do so with extreme care. (Remember, your legs will be extremely close to that jackshaft!) Doing so will result in a huge increase in pep at high speeds and the need for carburation adjustment. If possible it is also a good idea to put ram air ducts to channel the flow going to the intake system.

NOTE: Nitrisoxide is only a good idea if you wish to kill yourself!!!!

Carburation & gas channeling systems The carburation systems main purpose is to mix air and fuel to the proper ratio (varying from 6:1 up to 14.7:1) for combustion within the engine. Air channels or manifolds guide the mixture to the head of the engine, down to the valve port and into the combustion chamber. The common problem with most 50 and 70cc engines is a size issue. Not with the motor, but with these two components. Most 50 and 70cc mopeds are designed to go only 45k.p.h. which is sickeningly slow for either engine. Thus the engineers put on small carbs to limit airflow and in turn, slowed them down to regulation. As for gas channels, they often left them big for upgrades and porting, but air constriction is still often a problem. The easiest way to correct the carburation problem is by upgrading to a larger carb. Most 50cc engines come with a stock 12mm carb. This not only limits speed, but acceleration is also greatly effected. A 17 or even 19mm carb is much more advisable. Especially if a high pro flatslide big air carb is available. For 70cc engines, you can go as far as 22mm, dramatically increasing horsepower. But as always, a larger carb also means larger gas consumption, which could be a thirsty problem for small gas tanks. You may also overhaul the original carb if resources are thin and a replacement isn’t possible. Simply replace the main jets with equivalent sized base jets that has a larger inside bore for more fuel. This however will not solve any problems with airflow constriction, and will require carburetion adjustment to lean it out more. If you change out the carb, chances are, you will need a different manifold to suit. It is advisable to get a manifold to which has been flowed, honed or born- out. This improves gas flow and lessens constriction giving your moped a more responsive feel and even more horsepower. Another trick is to port the engine head and widen the gas channels going to the valve. But note: BE EXTREAMLY CAREFULL! I don’t advise doing this if you can’t get a replacement head. You can screw it up big time if you aren’t careful. Displacement & piston Displacement is a term used to describe the volume of gas displaced by the piston in the cylinder from B.D.C. (bottom dead center) to T.D.C. (top dead center) within the engine. The piston is the aluminum “cork” that moves up and down in the cylinder, translating linear motion into reciprocating motion via crankshaft and connecting rod. The easiest way to get more power from your motor is to either over-bore the cylinder or switch out cylinders with a larger size. (Switching cylinders also means having to switch cylinder heads too.) To do either operation requires a new piston of which is best bought in a kit. It is wise to adapt your order to current and future alterations. This can demand certain qualities of which the piston will need to comply. Such alteration list as turbo charging, nitrous injection, a tricked out crankshafts, extended cam height of which can result in your valve going through the piston… bottom line, be careful with your order. When over-boring a cylinder, take into account you will need to maintain a . 002 piston to cylinder clearance. In cases such as these, it is best to leave it up to the professionals so that you don’t end up with a cone instead of a cylinder. It is also possible to change displacement by ordering a special crankshaft that has a deeper draw than the standard stock shaft. These are quite finicky though and can sometimes cause extensive vibrations shaking your bike to pieces. Crankshaft & connecting-rod assembles The crankshaft is what converts the linear motion of the piston into the rotary motion required to spin your wheels. The connecting rod is what connects the piston to the crankshaft and in some models, supplies oil to the piston pin and pin boss. The only way you can alter engine performance via connecting rod is by ordering lightweight rods. But watch out, you mustn’t sacrifice strength for lightweight shiny things! If a rod snaps… YOU’RE SCREWED! As for crankshafts… There exist some lightweight race crankshafts available in kits. They take a few pounds off your bike but not much else. There have also been available, crankshafts that alter displacement by extending the stroke of your engine. It is my experience, these only serve to shake you and your bike to pieces and wreck your bottom bearings. Be warned!

Camshaft Camshafts are what operate and control the lift of your valves. They can be located in the head of the engine (O.H.C.), or they can be positioned within the lower end of the engine, push rod style (O.H.V.). Camshafts without much lift and lift duration often severely limit the passage of gasses within a motor greatly effecting efficiency and horsepower. It is advisable to obtain a camshaft with a higher and longer lift to increase gas flow and horsepower noticeably. It can also be a good idea to change the timing chain and sprockets when you do this to ensure the chain doesn’t snap due to the new shaft. Flywheel & electronics The flywheel on a moped serves 4 functions. The first is to store kinetic energy/ momentum to help drive the motor through all 4 strokes. The second is to serve as a harmonic balancer and absorb vibrations from the drive train. The third function is to house the magnets for the charging and ignition system. The fourth and final function is an R.P.M. limiter via ignition retardation. It is the fourth function of the flywheel that limits the engine to about 7000R.P.M. thus limiting your speed. The downside to this mechanism is that by retarding the spark, the engine is lit later than it should be and throws more heat out the exhaust, resulting in burnt out exhaust valves. The solution to this problem is to retard the retardation devices by welding them in place or by whatever means necessary. Doing this will allow your moped to reach 8500R.P.M. on the road! Another good way to get a few more R.P.M. out of your motor is to purchase an advancing flywheel, which allows for the flow of more gasses into the combustion chamber before ignition. Thus you’re engine will now scream. (As will you if you if you’re oil pump suddenly quits!!) If you are going to tamper at all with the R.P.M. and electronics, ignition systems on older mopeds can often be finicky and costly. It is best to switch to lightweight C.D.I. ignition instead of using a point’s ignition set. This also allows you to put on a speed limiter for regular street use. If you do not use a C.D.I. ignition set, it is advisable (pending on the year) to service or even replace the points ignition relay system. It can save you a big headache down the line.

Bearings The bearings are what allow the smooth frictionless turning of every component in you’re engine. If you’re going to go all out on beefing up you’re engine, it is far worth the expense of getting a bearing kit and replacing every possible bushing and bearing that engine’s got to offer! There’s nothing more frustrating than when a $15 bearing goes and it costs you a new shaft… or your life!! Clutch The clutch is the device, which engages the motor at the right time, and disengages it during shifting or stopping. By doing this, it allows the engine to run even at stoplights. The only way to get more power from your motor via the clutch is by removing weight from the clutch. This engages the clutch at higher R.P.M. resulting in a quicker pickup. Because of this though, you will burn through clutches quicker than normal. With wet clutches this can pose some problems due to clutch dust floating within the oil. Gearbox The gearbox or transmission is what takes the power off the clutch, gears it down and supplies it to the head sprocket at the rear of the transmission case. Some have only a single speed, some have as many as 5. Some shift automatically, some don’t. Transmission work is relay quite finicky and I don’t advise you do much. Besides, there isn’t much to do because there isn’t much to change or customize. All I advise you do is change the bearings if you’re brave and change the gaskets when needed.

Sprockets A sprocket is the gear that drives or is driven by a chain. Mopeds have two, the drive sprocket is the one that comes out the transmission case and the rear sprocket is attached to the rear wheel hub. Changing sprockets is the most essential things you should do after tuning your moped to the degree listed in the above. Your engine will get much more power from the tune, but will only go faster if you don’t change the sprocket ratio. The best way to set up you’re bike is to set it so that (under normal riding conditions) the bike will barely top out at is maximum R.P.M. on a flat track. In other extreme conditions such as hilly countryside or gravel roads, you would want to switch to a far torqueier sprocket and take it down by about 5-7 teeth. This will make you accelerate quicker, but you will also top out at a much lower speed. Remember, its all a mater of preference. Exhaust The exhaust system is what muffles the sound of the gasses being expelled from the engine, and guides it to the back of the bike. (So as not to gas the driver) The system also constricts the flow of the gasses causing backpressure, which is essential… in small quantities. Most modern exhaust systems tend to supply too much backpressure, which leaves a lot of exhaust still in the combustion chamber affecting the efficiency of the next cycle. A header is the extreme option for getting horsepower from the exhaust, but most noise regulations would not permit such alterations. What is better is to create a larger channel pipe going from the engine to the muffler for air space. Or if possible, run duel exhaust with the same concept. I guarantee there will be some improvement in your engines performance. Lubrication systems The lubrication system is the basic lifeblood of your engine! It provides and applies a medium of friction inhibitors (oil) on all moving parts, preventing premature wear and thermal seizures. Whether by the splash method, oil- slinger method (an adapted form of the splash method), by oil pump, or any combination of the 3 listed, the lubrication system is what keeps your engine running longer than a tragic 5min. Before you altered the flywheel ignition retarders, you must take into account whether or not your lubrication system will accurately be able to cope with the sudden new burst of R.P.M. If you don’t, you may: A: Produce enough oil pressure to blow just about every oil seal on your machine. (Resulting in a thermal seizure) B: Suck bubbles into your oil pump C: Just plane old blow your oil pump. D: Not get enough oil for the splash effect to lube your motor resulting in a thermal seizure or damage. E: Whip your oil into a froth resulting in B, C and D. Need I say more? When altering engines always flush the motor and oil thoroughly to ensure metal flakes chips and dirt are not floating around somewhere within the engine. Only use high quality oil when running, and chose oil viscosity wisely. You do not want oil that’s too thin or else it won’t protect the engine properly and cause premature wearing of parts. You also don’t want an oil that’s so thick it wont flow into the top end of the engine, causing a potential thermal seizure or at the very least, the premature wearing of parts due to lack of protection. Use you’re discretion and version of owners Manuel to pick the oil viscosity, and running synthetics is also a good idea whatever the cost. Keep in mind, a jug of synthetic costs $15. A new piston, cylinder, connecting rod, bearings, etc… you get the picture. DON’T CHEEP OUT OR IT’LL COST YA!!!!!!!!! Spark plugs Spark plugs produce the spark required for ignition. They are often very durable (when left in the engine) and are hard to foul except for in extremely leaned out or richened engines. It is essential to use either factory recommended plugs or specially rated race plugs for risk of overheating the piston or cylinder sleeve. Split fire pugs are a great way to increase firing efficiency and lower emitions, they do however produce excessive heat. Change plug types only under careful advice and proper carburetion adjustment. Proper maintenance In the end, it all comes down to this. You treat you’re toy good, it’ll treat you the same way right back. IT’S THAT SIMPLE! JUST TRY IT! The oil The best and easiest way to keep your high performance machine, running like a high performance machine is simply to just change the oil often. Many mopeds have an oil submerged or “wet” clutch that constantly sheds clutch- dust into your motor’s lifeblood… IT’S OIL! These particles float around within you’re engine’s oil reeking havoc on your bearings and cylinder walls, causing premature wear and the clogging of oil galleries. Over all, it’s far worth the oil change. I personally recommend twice a season at the least! The more the better! Greasing As with oil changes, greasing is also vital to the survival of you’re moped’s vital parts. The swing arm, suspension components, axles, wheel bearings, speed’o drive, head tube bearings, cables… any thing that moves can use a shot of grease! Even the kickstand!! It is wise to do this only once a year though and only apply as much grease as needed. Overdoing it can result in blown seals, and even can impair your brakes if your not careful with the wheel bearings and speed’o drive. This will keep you bike from creaking like an old floor and alow you’re suspension to flowing, not bounce or seize. Cleaning Cleanliness is next to godliness… so clean your bike often!! There is nothing you can do to make the road any less filthy than it already is, so get used to it. (That is unless you work for Alberta infrastructure in which case I would like to have a little talk…) The paint job on your moped is delicate. It is essential to keep it clean of dirt, oil and abrasives to maintain a rust free, and a great looking moped. When a frame rusts, it dramatically affects its structural integrity, possibly crippling the frame and risking you’re neck! That is why it is important to cover up any paint chips or nicks taken out of the frame. Nail polish is an excellent medium for covering up Chips, nicks & scratches, resulting in the ideal semi-permanent fix. It is easily sanded off and will often not damage surrounding paint when applied. It’s a good idea for the bike and your neck! Fixing fundamentals When fixing anything, remember these four fundamentals for any job: 1. “Cleanliness is next to godliness” –meaning if every aspect of your workspace (or life for that mater!) is organized and clean, you’ll be rewarded by taking mechanics to a whole different level… Where its easy?! 2. “An attention to detail is essential” –you cant expect yourself to fix something if you don’t pay attention. The inability to pay attention to the disassembly will then result in the inability to figure things out for reassembly! It’s that simple! You must also keep a keen eye for cracks and wear marks to learn of other possible problems, which left untouched could result in fatigue and failures consequently larger problems than the initial infringement. So long as parts are checked, cleaned and well lubed, most problems are easily repaired. Remember, the more you simplify the task, the easier it will be… there are few acceptations to this rule… (Even with Suzuki’s!!) 3. “Simplify what you can, and your job will be… SIMPLE!!” Do whatever it takes to simplify what it is you are doing! You will only be rewarded by your attention to detail. 4. “Take pride in what you do!”-or else, what’s the point?! General engine repair theories Given the previously listed fundamentals are taken into account, there are just a handful of extra theories to memorize. -If it doesn’t go on, don’t force it! If a part will not turn, come off or go back on, chances are… THERE’S A REASON! Check for missed bolts, rust, debris and sometimes-even welds that may be caught, snagged or other wise in your way. -If the tools don’t fit, DON’T USE E’M!! if a socket or wrench fits quite loosely and can be rattled around on the bolt head or nut, grab the right size! It’s not worth the headache of trying to get off the bolt you just stripped!! -To take a hammer or screwdriver to chrome or a machined surface is murder!!! Never use a screwdriver to pry at machined surfaces or whack off chrome covers with a ball-peen hammer! Doing so will only result in a badly marred and disfigured part! This not only impairs performance, but the general aesthetics of your machine too.