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Small troubleshooting Engine Repair and Tips

Three step approach Determine why a small engine will not start or run properly. Welcome to Find N Choose, your free information site.

Fuel - Spark - Compression A gasoline engine needs the following three essentials to "run"

In time problems develop with fuel delivery, spark or compression, it only takes one of these to fail to prevent an engine from starting or to run. The first step is to determine which of these is at fault.

Three Step Trouble Shooting

Spark

Place the engine out of bright sunlight, remove the spark plug, reconnect the ignition wire to the spark plug and lie it on the engine head, or metal of the engine, where it makes a path to ground of the engine. Give the rope a tug and observe whether there is a good spark jumping the spark plug electrode gap. A good blue spark is ideal, If there is no spark, try changing the spark plug, and try this test again. No spark indicates ignition problems.

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Note the colors and sound to the spark.

A fat blue spark that cracks audibly indicates a very good spark. A white spindly sparks indicates a problem in the spark producing mechanism (check grounding of spark coil first) A reddish sparks usually indicate burnt points, or a failing condenser. A weak spark may not ignite the fuel-air under compression. If there is a spark, the problem lies either in fuel delivery, or in the compression of the engine.

Spark plug

The spark plug provides a path within the to provide a gap for the spark to jump which ignites the fuel air mixture. Spark plugs have many heat ranges. The manufacturer of each engine decides which heat range is best, to provide the optimum operation for each engine type. The heat range of a new engine is usually on the cooler side of the available heat ranges. The proper range will keep the spark plug clean of carbon and other components of combustion. As an engine wears and the compression drops and oil rings wear, the spark plug may not be hot enough to deal with the different gases and burnt oil in the combustion chamber, caused by oil leaking past the oil rings of the . A spark plug of a greater heat value will help keep the sparkplug cleaner. Each spark plug has a certain size thread and threaded area. If the spark plug does not reach far enough into the combustion chamber, the result is poor starts, poor combustion, and less power. If the sparkplug thread is too long, the spark plug will reach too deep into the combustion chamber and will not leave enough room in the combustion chamber for the piston to travel. The piston will strike the end of the spark plug, and damage both the spark plug and the top of the piston. It is important to choose the right spark plug for each individual engine.

Spark plug gaps are around thirty thousands of an inch (.030). To remove the spark plug from the engine, turn the spark plug counterclockwise. To clean off heavy carbon particles, use a tiny screwdriver, or knife, and scrape off the carbon, on and around the spark plug electrode, finish up with a small wire brush. When replacing the spark plug, do not over tighten. The spark plug on an aluminum head can not be tightened the same as a cast head. If you over-tighten, on aluminum heads, stripped threads could result. Spark plugs can last a long time on an engine that is in good shape. On older engines with lots of wear, burnt oil in the carbons up the sparkplug. The spark plug needs replacing sooner in older engines. Spark plugs are not too expensive and it is worth replacing every couple of years, as this will help to insure easy starts, greater power, and cleaner running.

The condition of a spark plug tells us a lot about the condition of an engine.

Normal Spark Plug The color of a normal spark plug is brown to a grayish tan.

Worn Spark Plug A worn spark plug is normal in color, but has rounded electrodes, and a large electrode gap.

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Carbon Deposits

A spark plug with dry sooty deposits indicates an engine with the fuel-air mixture too rich, or a weak ignition. This condition can cause hard starting.

Ash Deposits

A spark plug with a light brown deposit on the electrodes is usually caused from oil leaching into the combustion chamber, or additives in the fuel. Over build up can cause a mis-fire.

Oil Deposit

An oily spark plug indicates oil is leaking past piston oil rings or work valve guides. This condition causes hard starting, or no starting.

Bridged Spark Plug Gap Burnt combustion products lodge between the spark plug gap, shorting out the ignition. This prevents starting.

Overly Hot Spark Plug

A blistered, white electrode insulation, with no deposit of any kind indicate a too hot condition. Over advanced , too lean fuel-air mixture, or valves not closing properly. This can lead to melted and burnt valves. Check for correct spark plug heat range. Preignition is a product of too hot a spark plug, check for over advanced timing, or a too lean fuel-air mixture.

Spark Plug Glazing

Glazed spark plug insulation has a yellowish glazed appearance. A glazed spark plug indicated an engine running at to high RPM. The engine overheats and causes mis-firing.

Fuel

Smell it, it should not smell old and stale, or look thick and deep yellow in color. Old fuel loses the ability to vaporize. Gasoline left in the over the winter becomes stale and will not support combustion. Stale fuel can cause a stuck check-ball in the , and plug up fuel jets. Fuel left for a long time in a half full container, will vaporize out, leaving behind a thicker, staler gasoline, which will not support combustion as well, as fresh fuel. It is the vapor, which supports combustion, not the raw wet gasoline. If the fuel is stored in a very warm location, the fuel becomes stale in a shorter period of time. The smaller the amount of fuel stored, the quicker it oxidizes and becomes stale.

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Is the fuel able to reach the combustion chamber or is the or carburetor plugged? A quick test is to remove the spark plug, pour a tiny bit of fresh gasoline directly into the cylinder. Replace the spark plug and give the rope a tug. If the motor starts and runs briefly, fuel delivery is the problem. Because the engine runs, it verifies that spark and compression is okay. If the engine does not run, spark or compression is the problem. Take the proper precautions when handling gasoline, keep the container away from flame and sparks, keep the lid on the gasoline container when not in use, keep gasoline off skin. Use in well ventilated areas.

Compression

A quick test for compression is as follows, turn off the ignition and remove the spark plug. Place your thumb over the spark plug hole and give the rope a tug. You should feel the compression trying to lift your thumb off the spark plug hole. If there is, no compression or low compression, it is an indication of internal problems such as valve, rings or piston failure. If you have access to a compression gauge, and get a reading of around 65-70 psi., that is good. Any compression reading below 45 psi., indicates a well worn engine. Most four- engines in good shape, have a normal compression of around 75 pounds per square inch. (psi). Two stoke engines are around 90 psi. Engines with very low compression are very hard to start, and a very quick pull is required to get the compression up high enough to start the engine.

If the compression is low when you test with a compression gauge, try adding 1-2 tablespoons of oil directly into the spark plug hole. Try cranking over (giving the rope a tug) and re-test the compression. A rise in the compression indicates worn rings. No change indicates valves are not closing properly.

Reasons for poor compression can be, spark plug loose, bolts loose, cylinder head leaking, and carbon blocking valves from closing properly.

Note: There should not be any raw gas anywhere on the outside of an engine in good condition. Any leaks indicate a fuel leak, or a problem with the engine.

How a Primer Works

A primer, is a small pump connected into the fuel line, with a one-way valve within it, allowing fuel to move in one direction only. When you press on the primer bulb, fuel pumped from the fuel tank towards the carburetor forces the older fuel within the carburetor and fuel line back to the fuel tank. The new fuel entering the carburetor vaporizes easily, and causes the engine to start promptly. Any crack in the rubber bulb, allows air to enter the fuel line, preventing the primer from pumping. When changing a primer, take note of the direction installed, the primer has a one-way valve. It must be placed it in the right direction, or it will not pump. As the primer bulb ages, the rubber cracks or loses elasticity and will need to be changed.

Small engine timing

Most small engines, such as lawnmower engines have fixed timing at the factory, and are not adjustable. Small

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engines which have timing that is adjustable, the timing is adjusted 11-20 degrees before TDC (top dead center) depending on what the manufacturer calls for. If you put a thin piece of paper between the points and slowly rotate the by hand, when the paper just slips out, this is the point at which the spark plug fires.

Weed Eater No Spark

The spark is produced each revolution of the crankshaft by passing a permanent magnet (embedded in the ) past a coil of wire. When the magnets, passes the coil of wire, a current is produced in the primary windings (fewer windings) of the coil and then the collapsing magnetic field of the primary windings cuts through the secondary windings (large amount of windings). This produces a very large voltage at the spark plug, jumping the gap and returning through the ground metal of the engine, making a complete circuit of the spark coil.

The spark mechanism in the weed eater is a very simple mechanism and everything has to be perfect to produce a spark. Over time, rust and corrosion happen around the bolts that hold the spark mechanism in place. Try a new spark plug, before trying anything else, if this does not help; then disconnect the cable, undue the five bolts that hold the weed eater together and separate the unit. Unplug the wires to the stop switch.

Now with the unit on the bench take a few measurements with an ohm-meter. There is a primary and secondary wrap of wires within the spark mechanism. The primary windings have a low ohms reading, and the secondary winding have a high ohms reading. The important factor is to get some form of reading, no reading indicates that the wire inside one of the fields is broken, therefore the unit is defective. Typically, the primary coil will read 2-3 ohms and the secondary windings 8,000-10,000 ohms. The sparkplug lead is connected to the secondary winding. Even if you do not have experience with an ohmmeter, continue by removing the two hold down bolts and remove the spark unit. Use sand paper to clean the unit and bolts so you get a good contact between the spark unit and body of the engine. To re-assemble, Place the spark unit back on the motor and tighten down the two bolts slightly by hand, then place a business card or equivalent thickness piece of paper between the spark unit and flywheel, rotate the flywheel until the magnets attracts the spark unit. Tighten down the two holding bolts, then remove the paper, this provided the correct gap between the spark unit and flywheel.

This is also a good time to replace the starting rope. Do not remove the plate on the rope assembly, as a wound up spring can fly out and cause injury. Pull the start rope all the way out, then jam a nail of stiff wire alongside the unit to keep it from re-winding. If the rope is already broken, then wind up the spring mechanism by hand and jam in place. Remove the old cord, and fish in the new cord with a fine wire, attach it the same manner, as the old cord. Remove the nail that is holding the unit from turning and allow it to wind in the new cord. Put the motor back together again and check for spark. To put the weed-eater back together, reconnect the shut off wires, turn the drive shaft, from the lower end of the drive shaft (where the line goes), by hand to line up the spine where the motor connects to the drive shaft. Slowly slip the unit together again. Place the five bolts back into place. Move the throttle wide open and jam in place with a nail etc. Place throttle cable back in place, remove nail. A good fast pull is required to produce a good healthy spark.

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Magneto System With Points

As the flywheel turns, a magnet in the flywheel sweeps past the coil energizing the primary winding some 300 volt. This voltage flows through the closed points, and primary winding to engine ground. When the points open, the primary voltage collapses into the secondary winding producing 12,000 volts at the spark plug

If you need to work on a weed eater carburetor, purchase the correct carburetor . If you dissemble the carburetor, you need the exact gaskets, as the main gasket, is also a diaphragm, part of the gas delivery system. If the weed-eater is more than a couple years old, the fuel line will also need replacing as the fuel line gets very brittle (from the heat of the engine), and will easily snap in two. In a pinch, on occasion, I spliced in a new fuel line near the fuel tank, the fuel line remains more flexible for a longer period of time, near the fuel tank.

Chain Saw Problems

Chainsaw Will Not Start

Most chainsaws use two stroke engines because of their lightweight and high power output. The most likely cause for a chain saw not to start, is a fuel problem. Chain saws left for a long time with fuel in the tank, will result with a problem of the fuel supply needle sticking, or a dysfunctional diaphragm. Remove the spark plug and pour in a little good clean gas (no oil mix), directly into the combustion chamber, replace the spark plug and spark wire and give a pull on the rope. If the chain saw starts, fuel delivery is the problem. If it does not start, do a spark test. To investigate a fuel problem, dump out the gas from the tank, and fish out the flexible fuel line with the attached fuel filter in the gas tank. Form a wire into a hook to do this. Usually you will find that the fuel line has cracked, and is drawing in air instead of fuel. Replace it and the filter at the same time. If the fuel filter has become plugged up because of grime, replace the filter.

With chain saws, it is easy to introduce dirt into fuel tank while filling in the field. Carry a small one-inch paintbrush, when fueling up, brush around the gas and chain oil fill plugs before removing, this prevents grime from dropping into the tank when you remove the fill plug. Remove the carburetor cover after two or three tanks of gas and clean the , and near this area with the paintbrush. When an air filter gets plugged, less air is mixed with the gas, and a very rich mixture is created, which will wet out the spark plug, causing it to short out, the result is the engine will not start. A dirty air cleaner is the same principle as leaving the choke fully on.

Older chainsaws do not idle on their own very well because of wear of the seals, worn crankshaft seals allow air to enter the crankcase. Idling the chainsaw up a bit above normal can help.

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Other causes for not idling are a dirty air cleaner, plugged air vent in fuel tank cap, water in fuel, dirty or incorrectly gapped sparkplug, leaking reed valve, air leak at base of carburetor, dirty fuel mixture needle or incorrect adjustment.

Two stroke Engines

If a chainsaws is stored with gas left in the fuel tank, it can cause problems within the carburetor to the diaphragm and the fuel needle, which may stick, because the old fuel usually turns into a varnish like liquid. Old fuel diaphragms can dry, crack or tear. Build up of old varnished gas can also plug up the low and high speed fuel jets.

Fuel jets can usually be cleaned by using a small strand of wire, which is carefully passed through the fuel jet holes. Never use a hard material such as drill bits, the jets are soft metal and can be damaged. Primer bulbs sometimes collapse and will eventually crack stopping the flow of fuel. Replace them at the first sign of cracking. Compression of typical chainsaws should be around 120 psi.

Chainsaw Bars

Most chainsaw bars are reversible, and under normal home use, should be turned over once a year, this evens out the wear. To check the tension of the cutting chain, use moderate force, slide the chain around the bar, it should slide easily with no hard spots. A hard spot indicates a damaged chain or worn drive sprocket. Keep in mind a new chain will stretch a bit after 15 minutes of use. When you install a new chain, run the engine at a moderate speed for a couple of minutes, and then recheck tension. Do some light cutting and, recheck tension. Keep the bar lubricating oil topped up and front idle sprocket well greased. The chain should be free enough to easily turn by hand.

Chainsaw Chains

Brand new dry chains not oiled from the factory should be soaked in a few hours before installing on chainsaw, most new chainsaw chains do come well oiled.

Changing The Sprocket

To remove the sprocket lock nut, screw a plastic piston plug into the sparkplug hole to keep the crankshaft from turning. An alternate choice is to remove the sparkplug and stuff the combustion chamber with cotton clothesline. If you use air tools, there is enough quick blows to remove the nut without trapping the crankshaft.

Poor Power, Chainsaw

If your chain saw has poor power, remove the and clean out the carbon from the exhaust port (turn the engine over to get the piston below the exhaust port, so you don't damage the piston, while scraping out the port).

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Clean out all the oil packed sawdust in behind the muffles and in the cooling fins. Twenty-five percent of the cooling comes from the cooling fins behind the muffler. If the engine overheats it will stop running and will not start until it cools down. This is also a good time to clean the air filter.

Checking Reed Valves

Remove the air cleaner and start the engine. Hold a piece of white paper next to the air port. Oil spots on the paper indicate the reed valve should be replaced. Reed valves should not bend away from the mounting plate more than .010 inch.

When a chainsaw starts and runs for a long while, then stops and cannot be started, it is usually an overheating problem. If a chainsaw is overheated, the fuel starts boiling and this causes a vapor lock, stopping the delivery of fuel. In time, dirt and grime plug up the fins around the cylinder and head, preventing the engine to cool properly. To fix this you must clean the outer engine parts, as it was when it was new, then it will run again, just like new. You must remove the muffler to get at the cooling fins on the muffler side of the engine

CAUTION If the chain becomes loose enough to "jump" off the bar, shut the chainsaw off immediately! I once saw the results of one fellow who thought if he "revved" up the saw; the chain would somehow jump back into the track. Unfortunately the chain flung back into his face and cut him up badly.

Two-Cycle, Why Oil Is Mixed With Gasoline

The reason oil is mixed in with the gas in two-cycle engines, is to provide lubrication to the moving parts, as there is no oil reservoir, nor any pump to move the oil to moving parts. The oil-gas mix enters the crankcase and lubricates the moving parts as it moves towards the combustion chamber. The fuel-oil mixture has to be right to provide the proper combustion and proper lubrication. Too much oil and you will get a build-up of carbon, too little and you will have premature wear of the engine. If there is no oil mixed in the fuel, the engine will seize up. You must also use an approved two-cycle oil which burns cleaner than regular oil.

If you fill the tank of a two-cycle with regular gas by mistake, remove the fuel and fill with the proper oil-gas mix. No harm, is done, even if you have already run the engine for a short period (the oil deposited in the crankcase will protect it for a little while). If you fill the tank of a four-cycle lawnmower with gas mixed with oil for a two-cycle engine, it will not harm the engine even if you run it a short time. Drain it out and replace with clean unmixed fuel.

Small Gasoline Engine Runs A Short Time And Quits

When a small engine will only run a short period of time and quits, it probably starves itself of fuel. The most common problem is that the fuel cap vent has become plugged or damaged and no air can enter the fuel tank. As an engine runs, air must replace the fuel in the fuel tank, as fuel is drawn into the carburetor, a vacuum is created

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and eventually the engine can no longer draw fuel. Check the fuel cap. In addition, if the cooling fins on the cylinder and head are not cleaned out regularly, they can become plugged-up with dirt etc. causing the motor to overheat and quit. On a very hot day, the engine just may not be able to cool itself properly and overheat. Just let it sit in the shade for awhile and cool down before re-starting.

Stalls While Idling

Other causes for not idling; are, dirty air cleaner, plugged air vent in fuel tank cap, water in fuel, dirty or incorrectly gapped sparkplug, leaking reed valve on 2-cycle engines, air leak at the base of carburetor, dirty fuel mixture needle or incorrect adjustment.

Adjusting Low Speed Mixture - 2 and 4 cycle

Warm the engine to operating . Make sure choke is in the off position and air filter is in place. Approximate idle starting adjustment is 1 1/2 turn out. While running the engine at idle speed slowly turn the idle adjustment screw in until the engine starts to miss or slow down, back out slowly until engine runs smoothly, then back out 1/8 additional turn, this will prevent a too lean adjustment, and easier starting.

Adjusting High Speed Mixture - 2 and 4 cycle

If the engine has a high-speed adjustment screw, warm the engine to operating temperature. Make sure the choke is in the off position and air filter is in place. Approximate starting adjustment is 2 turn out. Run the engine at high operating speed and back out the high mixture screw until the engine starts to slow down, note the position of the mixture screw, then slowly turn in the high speed mixture until the engine starts to slow down. Note the position of the high-speed mixture screw. Adjust the high speed mixture between the two extremes.

Removing And Cleaning

Most small engines carburetors have two bolts holding it onto the engine. To remove, drain the fuel out of the fuel tank. Another option is to remove the fuel line from the carburetor and jam a tapered piece of wood or bolt into the end of the fuel line. Remove the air-cleaner, remove the carburetor hold down bolts and linkage. Take note of the linkage setting, as there may be more than the one setting (to mark, use a felt marker pen). Wash down the carburetor with some kerosene or varsol, using an old paintbrush or toothbrush. Take care not to get any into your eyes. Place the carburetor on a clean piece of cloth and remove the four bolts holding it together. Use a short (12-16 inch) piece of clean plastic gasoline tubing; Place over the small fuel delivery channels and blow on the other end with your mouth, this will blow out anything blocking the flow of fuel. To re-assemble, you will have to buy or make new gaskets. Stores like Canadian Tire or Auto parts stores handle this do it yourself product. A leather hand-punch can be used to make the holes in the gasket material. Place the carburetor back onto the engine in the reverse order that you removed it. Take note that two-cycle carburetors require a special material gasket that have to be purchased for each exact carburetor; it also acts as valves for the pumping of fuel. Generally, most carburetors can be cleaned on the engine by removing the needle valve (mixture adjusting screw), lock nut and o-ring. Apply compressed air to the needle valve opening. Small copper wire or monofilament can also be used to clear out carburetor passages.

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Lawnmower Backfiring

If the lawnmower engine backfires and will not start, after you pushed the lawnmower over a large rock or solid object, chances are the key in the keyway between the flywheel and crankcase sheared off and now the timing is no longer correct. To fix this you will have to remove the flywheel and place a new key in the keyway.

Running the engine over lean can cause carburetor spit-back on sudden acceleration. Other backfiring problems such as out through the muffler or carburetor, may be caused by extreme carbon build-up on the valves and valve-stem guides, this build-up prevents the valves from closing fast enough and far enough. The valves will not be able to contain the exploding fuel. This usually happens because the oil is hardly ever changed, it loses its lubricating qualities, becomes full of carbon causing harmful carbon deposits on the valves and guides.

Other reasons for backfiring are, dirty air cleaner, choke stuck closed, carburetor flooded, carburetor mixtures incorrect, dirty carburetor, exhaust valve sticking, incorrect ignition timing - if adjustable.

Lawnmower Engine Misfiring

Misfiring is when the fuel-air mixture is not ignited. The most common reason is a bad spark plug. Too rich or too lean a mixture can also cause a misfire. Sticking valves or poor valve sealing also cause misfiring.

Gasoline Engine Surging

Engine surging is when an engine alternates between running fast and slow at the same throttle setting. The most common reason is a partially plugged fuel tank vent. A dirty air filter can also cause this problem. A sticking air vane speed control can cause surging.

Other reasons for surging are, fuel restricted to carburetor, throttle linkage or butterfly binding or sticking, carburetor mixtures incorrect, carburetor float level to low and speed governor sticking or binding.

Stalls On Acceleration

Reasons may be dirty air cleaner, dirty fuel filter, incorrect fuel mixture settings or damaged fuel mixture needles.

Lacks Power

Reasons may be, dirty air cleaner, loose spark plug or spark plug ignition wire, low oil level, dirty spark plug or incorrectly gapped, choke partially closed, carburetor mixture incorrect, carbon blocking muffler or exhaust port, ignition timing incorrect - where adjustable, oil seals leaking on 2-cycle engines.

Reasons For Engine Knocks

Equipment loose or improperly adjusted

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Excessive carbon in combustion chamber Loose flywheel key or flywheel nut Overly advanced ignition timing Loose or worn Worn cylinder Broken piston skirt Broken

Ads by Google Small Engine Repair Engine Natural Buy Engine Oil Some engines use a soft key on the flywheel and can have a partially sheared key from hitting something. This can cause the timing to be off and cause hard starting.

Removing Flywheel

To get at the points and condenser you have to remove the flywheel. Do not hit the flywheel with a hammer; you will damage the flywheel or other parts of the engine. Hitting the flywheel with a hammer will reduce the strength of the permanent magnet embedded in the flywheel and will cause reduced spark at the sparkplug. Do not try prying it off with a screwdriver, as you will probably crack the engine casing and warp the flywheel. Use a proper puller designed for the job, which will pull it off with proper balanced forces. To remove the nut holding the flywheel in place, use an air or electrical driven impact tool and turn the flywheel nut in the opposite direction of crankshaft rotation. Do not try jamming a screwdriver into the air blades to keep the engine from turning over and attempt to use a wrench; you will only end up breaking some blades off the fan blades.

If you do not own impact tools, try this. Place a few drops of penetrating oil on the threads, then take a boxed end wrench and rotate the crankshaft until you can feel the compression-taking place. While holding the wrench in this position, give the outer end of the wrench a whack with a hammer. The compression may hold the crankshaft just enough to dislodge the nut. An alternate way is to remove the sparkplug and stuff cotton clothesline inside the combustion chamber; this will prevent the crankshaft from rotating.

Reasons For Overheating Gas Engines

Excessive engine loading, especially on very hot days low oil level or wrong viscosity oil Cooling air flow obstructed or clogged cooling fins Lean air-fuel mixture Ignition timing incorrect Carbon in the combustion chamber Running the engine at too high a revolution for a prolonged time

How To Remove Carbon From The Combustion Chamber

Try using a fuel additive to help remove carbon first, if this does not work, then go the manual route to removing carbon. Remove the cylinder

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Rotate crankshaft so piston is top dead center, scrape away carbon with a scraper (small putty knife) and brush away carbon with a wire brush. Be careful not to remove any metal. Do the same to the cylinder head. Rotate crankshaft and inspect valves for wear or damage Compare new head gasket to old to confirm it is the right one. Install head gasket and cylinder head and start the holding bolts by hand. Then while cross tightening (first one side, then the opposite side) to manufactures specified tightness, in increasing tensions. Do not tighten each bolt all at once as this can warp the head

Valve Clearance

If the clearance is too great, the engine will be noisy (loud tapping). This can cause wear to and valve lifters in the contact area. Push rods can become bent. is changed, resulting in poor engine power.

Valve clearance clearances are set with a feeler gauge. Spec sheets provide the information for each particular engine. If the clearance is too little, valves will not seat properly and heat will not be transferred properly resulting in burnt valves, low compression and poor engine power. Check manual for correct clearances. Typical clearances is .006 intake, .012 exhaust.

Adjusting Points

On most small engines, the points are located behind the flywheel. If the points are located behind the flywheel, remove the flywheel and remove the spark plug; this will make it easier to turn over by hand. Rotate the crankshaft until the points are open their fullest. Using a feeler gauge, adjust the point gap so the feeler gauge just slips between the points with a little friction. If you are setting them to .020; then 022 would feel much to tight and 018 would just slip in way to easy. Follow the correct point setting and timing specs for each engine. Note, oil acts as an to electrical current. If oil settles on the breaker points, its high resistance will prevent electrical current in the primary circuit. There is a seal on the point plunger to prevent oil from entering the breaker point area. A seal can be added if there is not one. The contact surfaces of the points must match exactly and squarely; adjust if necessary.

Testing Condensers

The condenser is constructed of a metal foil strip, which is wrapped in a circular fashion within a metal case, but insulated from each other. The tin foil accepts an electrical charge and holds it for a while. If there is a short between the metal foil and outer case, or the wire lead is broken, the condenser is bad. A quick test to determine if the condenser is good, is use a millimeter and set it on the highest resistance range ( X3). Touch the meter probes onto the case and center lead of the condenser; you should get no short reading, any reading is bad. Now reverse the meter leads, touch the case, and lead again. The voltage within the meter will have slightly charged the condenser, if it is good. The meter arrow should deflect momentary indicating the condenser did hold a charge. Each time you reverse the test leads of the meter to the condenser, a small bounce deflection of the needle of the test meter should take place. Blackened breaker points is an indicator that the condenser is bad.

Rusted Metal Gasoline Tanks

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Gasoline tanks that are rusted will eventually plug-up the jets in the carburetor. To clean out the rust, sand blasting is the best option. I have at times just removed all the gasoline from the tanks and flushed it out with water, added about a cup full of clean water with a drop of liquid dish soap, placed a handful of 3/4 inch or smaller, crushed rocks into the tank. Placed the lid back on and shook it until my arm felt like it is going to drop off. The rocks bouncing around will knock off the rust. Dump out the rocks when you are finished, flush out with water and let dry before re-installing on the engine.

Changing Oil

At least once a year you should change the oil (lawnmowers) when used once a week over a period of four months and more often with heavier use. The oil reserve in a small engine is about a liter of oil, or less. There is no filter to help clean the oil, so it becomes saturated with carbon and burnt particles. The lubricating qualities are lost and this causes rapid engine wear. To drain the oil, locate the drain plug on the lower part of the engine and remove. Drain into a container, replace the plug and refill with clean oil. Check the dip stick several times when filling, so as not to overfill. Motor oil becomes problematic at about 400 degree F; don't overlook the importance of keeping the engine cleaned to reduce the build-up of heat.

Choke Adjustment

The choke must be adjusted so that you can control the choke to fully open and fully close. To adjust, loosen the cable hold down bracket near the carburetor and slide the choke cable either up or down to get the full action of the choke. When starting an engine do not leave the choke on too long as raw fuel left in the cylinder will dilute the oil around the piston, which can cause piston scuffing because of insufficient lubricating.

Keyway

The crankshaft on most small engines is secured to the flywheel by a key within the keyway on the flywheel. If some traumatic force, such as a lawnmower blade hitting a rock; bends the key in the keyway the key may become bent or broken. Even a slight bending of the key can cause the timing of the spark to change, resulting in hard starting or not starting at all. When checking the key and keyway, check for cracks on the crankshaft and check the condition of the key. Replace them if you find any major damage. The tapered sections of the crankshaft and flywheel, must be clean and smooth, with no play between the two. Any slight burrs can be removed with a file. Check for any play or wobbling when the flywheel is placed on the crankshaft, it should fit firmly. If you have doubts about the condition of your flywheel key, replace it. It's not very expensive.

The maximum speed of small engines is 3600 RPM.

Horsepower One is the ability to lift 550 pounds 1 foot in 1 second or 33,000 pounds 1 foot in one minute.

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Typical Point Setting American small engine--- .020 of an inch West Bend ------.015 of an inch Foreign makes ------.012-.016 of an inch

Typical Flywheel To Armature Gap

Outboard Armature to flywheel clearance ---- .006 of an inch Under flywheel Armature to flywheel clearance ---- .012 of an inch To test clearance on a under flywheel, use a strap wrench to hold the flywheel when removing the retraining nut. Wrap the armature with two layers of black electrical tape without stretching too much. Place the flywheel in place and you should feel a little friction when you turn the flywheel. Remember to remove the tape when the testing is complete.

Heat

Large quantities of heat are produced in the combustion chamber, where can reach 2000 degrees F. A third of this heat is used for work, a third goes out the exhaust and the other third heats the engine.

Lean Running

- a slow falling and building of engine RPM - Lack of power - Carburetor spit-back on sudden acceleration - Engine picks up speed with choke slightly on - spark plug porcelain bright white

Rich Running

Black smoke in exhaust Black soot on sparkplug tip Lack of power

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