This must be a challenging problem, because I've taken my kid's 125CC Coolster back to the dealer twice and both times he "thought" it was fixed. Or I dunno, maybe he's taking me for a ride... anyway... it usually fires right up on a cold start, but after a few minutes it dies out and then, there's no spark or a very weak spark. The dealer replaced the CDI, then the coil and the ignition switch. After none of that worked I changed the stator. From what I can tell reading the other threads, one of those items should have been the problem, but... no dice. Anyone else encountered this, and if so, any advice on what to try next?

 

Firstly, I assume one of you changed the plug? Are you sure it is the spark, some machines look to have a feeble white spark but run OK. A blocked tank vent or fuel line etc, can cause these symptoms. A faulty choke can cause the engine to run rich, fine when cold, kills the engine when hot. If it is electrical, wire connections can warm up and fail, or a faulty regulator can overcharge and cause problems, that is more common on the "big stuff".

 

try unplugging the kill switch wire from the cdi. This will eliminate any faulty kill switch. had similar problem that turned out to be a switch

 

It could be your cdi box, I've ran into this issue before it would run fine then when warmed up would cut off and not start till it cooled back off. Turned out there was moisture in the cdi box and when it warmed up it would short it out. Swapped out the Cdi and no issues.

 

I've ordered another CDI, maybe that will help (the dealer said he tried that first, but who knows - zero faith in him at this point). It's definitely a spark issue, though, not fuel related. At least twice now I've seen good spark, run it for a few minutes, it died, then I pulled the plug to check again and spark was very weak or non-existent.

 

Yea, not all but most dealers are shady in my oppinion. Let us know the results when you get the cdi put on.

 

Did you ever find out what the problem was? I just replaced the entire wire harness, stator, coil, cdi box and rectifier and it starts up fine but as soon as it warms up I lose spark completely!

 

Hey did you fix the problem mine doing it

 

never heard of that. but this seems interesting. subscribed

 

No luck this far. I am at my end with it, I started it today and it runs fine for about 2 minutes then dies, no spark at all, then if you wait about 5 minutes it will fire back up and die sooner and sooner each time.