Been using a YX140 with VM26 for about six months now, but I've having more and more issues starting it and keeping it running. :(
When I first installed the engine it ran very well (after dropping the needle 1 notch).
I took it on a long, 160 mile trip a few weeks after installing the motor (~50mph with 16T sprocket) and that's when the problems started. Long story short the CDI I was using during the trip started to deteriorate and I almost never got it home. Upon popping a new CDI in at home bike started right up but never ran the same (putting the old CDI in caused the bike to run really, really bad, so I'm pretty sure that one was just toasted). I have tried probably 6-8 different CDI units, all of slightly varying physical appearances (seems like most of these Chinese CDIs are the same!) Most of them will start the bike cold but only run for a few minutes until abruptly dieing. It's nearly impossible to get it started again until cold. I have also tried two Honda CDIs -- one from an ATC and the other from a CT110. Both do the same thing.
I do have ONE CDI however that starts the bike pretty much every time. It will also sometimes abruptly die unless I adjust the idle strew high, but for the most part it's fine and definitely works better than all the rest. This CDI has a larger frame than the others and looks to be of the DC variety... (running AC directly from Lifan ignition coil)
Other things to note:
- Choking the carb even slightly has always caused the motor to abruptly stop. I have tried pilot jest from 17.5-27.5 with little or no difference.
- I have used a couple different coils and they make no difference.
- Valve clearances have been checked and set several times to .003 and .004 intake/exhaust.
- There is never any kickback on the kickstarter anymore.
Anybody have any ideas? I swear this thing is possessed!