Motorcycle Repair: ty 125 problem, premature detonation, mechanical failure

Question
hi michael

i own a yamaha ty125 which i cannot start for love nor money
it was running and just spluttered and died
it then started again but ran very roughly for a few mins and died again

i've cleaned the carb  checked for a good spark checked for petrol and mixture also cleaned air filter and everything seems in order

any ideas   hope you can help  cheers

tony

Answer
Tony,
 If you are getting a good stong blue spark and it is TIMED CORRECTLY you are dealing w/ either a fuel delivery problem or an internal mechanical failure problem.  Be absolutly sure your carburator is set correctly.  By this I mean that the floats are set at the proper hieght (there is a spec. for this in the manual), that the needle valve is not stuck and working properly, that the main needle is not damaged and that any orrifaces are not damaged by someone using wire or picks to clean them out.  Only solvents and compressed air should be used to clean these.  If you are still having problems you may need to investigate internally.  It is possible through premature detonation you have damaged the piston to the point where it may have a hole in it. Let me know what happens and we'll go from there.

Mike