Can’t figure out why this bike won’t fire. It’s a Loncin 125cc motor, don’t know what the quad actually is cause the name plate is gone. It has good spark, compression and fuel but will not fire. Timing is right and valves are within tolerance also. Only thing I can think of is something electronic or a sensor is telling it not to fire? The bike used to run and ran well.

Any help would be appreciated guys, I’m at a loss here.

 

If it has a spark, good compression and the timing is right, the only thing left is fuel. It has to be the right air/fuel ratio. Fit a new plug "just in case" then give the carb a good clean out and try again.

 

 

Don't alter air fuel screws unless you have to. I just blow the passageways and jets out with compressed air. This works 99% of the time.