Question about Motorcycles
Not completely sure I understand the question but I'd surmise the top of the piston faces the business end of the spark plug that is typically screwed into the top of the cylinder?
How Engines Work - with cool animation!
Hope this helps!
Posted on Nov 24, 2013
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Posted on Jan 02, 2017
Yes, the arrow should be facing forward. It is possible to find a small amount of oil in the crank. If the previous owner were using an odd oil/gas ratio like 32gas/3oil instead of the normal 32/1. The proper mix is four ounces two stroke engine oil to one gallon of gas. The more oil in the gas, the more oil in the crank. This odd mix usually happens if the owner doesn't know the proper mix, guesses the mix at the pump or just doesn't care what goes in so long as the bike still runs.
If you found condensation on the piston then the crank would have likely received the same blessing. Check the crank bearings.
Hold the flywheel in your hand. Lift it up and down then move it left and right. Any movement or is it rock solid? If movement then you will need to take the gearbox apart and install new crank bearings and seals. Put the old cylinder and piston back in place without the head for a moment. Put the bike on blocks so that the rear wheel is free to turn. Have someone rotate the rear wheel while you work the clutch and gears. If the gears don't want to shift smoothly then plan on installing a new shift fork or two. Now would be a good time for a new sprocket shaft bearing and seal as well. Don't forget a new foot shift shaft seal.
While you are doing repairs, de-carbon the head and cylinder. Run the piston down and check the exhaust port. Over the years carbon may have built up in the port and plugged it nearly closed. It should be about the size of the intake port. Remove the buildup to allow the engine to breathe.
Remove the water trap bowl at the bottom of the petcock, (gas valve). Is there any water or trash in the bowl? Drain a cup of gas from the tank. Is there any water or trash in the cup? Dump it, clean it and re-mount it, ( not all bikes have a water trap bowl ). Install an in-line fuel filter. Install a new stock NGK spark plug.
Drain and clean the carburetor. There should be a screw on the lower side of the carb float bowl. Remove the screw then replace it after the fuel drains. Remove the float bowl and clean the entire carb with a spray carb cleaner from the auto parts store. Wear protective goggles to avoid getting spray in your eyes. Spray into all the little airways and fittings in the carb. Remove the idle screw and the air screw on the outside throat of the carb and spray into the screw holes as well.
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Be sure to put these two screws back in the same hole they came out of. IMPORTANT > do not tighten these two screws down. Only screw these in until they LIGHTLY seat. Now turn each screw one and one half turns outward. Put the rest of the carb back together, clean the air filter and install the carb. Let the float bowl fill then start the engine. This process should get you back on the road.
I know this answer is more info than you asked for but I don't want you to have to go into the case more than once. Congratulations, you just rebuilt the entire engine.
Please rate this answer. Thanks Paulette!
Posted on Apr 22, 2009
Just to confirm with you... looking for a piston kit, barrel, and topend gasket kit for your 1991 kx125?
Where in the world are you?
Posted on Jul 14, 2009
SOURCE: how to change kx 125 2005 piston
You will have to remove the head and cyclinder to do this. You will need a manual on top end rebuilds for you bike.
Posted on Sep 28, 2009
Testimonial: "thank you for the information you sent it was very helpful as it will be the first time we have tried a piston change , , , thanks very much , riki"
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