Two-wheeled, motor-driven transportation, including mopeds and scooters.

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I cannot get my Honda X8R 50 cc moped started?

I have just changed my crankshaft. the scooter worked perfectly before i changed it, and everything is ok still. there is great compression in the cylinder, every gasket is ok, and there is a clean blue/purple spark, it just will not start.... there is gasoline spewing through where the exhaust goes on too. sometimes if i turn the engine for a while, it kicks back, and there will pop a big flame from the exhaust, any help?

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Sounds like a timing issue.

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Krisjan F, try this. Remove the airbox and filter. spray some carb cleaner into the carb throat. Close the choke and try to start the engine. If it fires, you have a fuel problem. start at the gas cap and clean the vent. Next, make sure the tank is clean and the gas is fresh and mixed to the correct ratio. make sure the filters and valve are clean in the petcock. check the fuel lines for any kinks or blockage. remove and thoroughly clean the carb, useing a piece of wire and carb cleaner.

if it does not fire, then you have either an electrical, or a compression problem. remove the spark plug. insert the spark plug into the spark plug boot. hold the base of the plug against the engine block. Turn the engine over as if you were starting it up.

Then check the magneto. points are a very common item to fail. and most times its because they are dirty, or out of adjustment. clean them with an emory board or a point file. An average gap to set the points to is .014"-.018". Coils rarely ever go bad. but, if the magneto is full of rust, every thing needs to be taken apart and cleaned.

if it has spark, then you have acompression issue. all 2 strokes must have at least 120 lbs of compression to run. Use a gauge to test the compression. If less than 120 lbs, you must find where it is going. The usual places are, rings, head gasket, cylinder base gasket, intake manifold (where it mounts to the cylinder), or crankseals. If compression is higher than 120 lbs, pull the exhaust system off and make sure the port and the pipe are clean. These two things will prevent starting. Hope this helps, good luck.

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check the wood ruff key on the generator side of the crank is in place and not slide out when you put mag on as this will give you serious timing issues, also be worth cranking the bike over with out the air box on it but place your hand over the intake of the carb untill you feel fuel on your hand i.e you can see a trace of fuel on the palm of your hand remove hand and crank engine over on full throttle, see what happens.

Andy @ peds_in_motion

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