I am presently working on my grandsons LG50 quad. It starts right up and runs for about 10 minutes, then dies. Before it dies, i can cover the choke opening and it will run for about 30 seconds, then tries to die again. Again i cover the choke opening and it will continue to run for about 15 seconds. After i keep it running by covering the choke opening four or five times, it finally quits and will not restart for about 10 minutes. When it quits, i have checked the gas,spark, and compression and all are good. I have tried spraying gas into the cylinder, but it will not start untill it cools down. I have seen simular problems in the forums but have never seen a solution. I have been an auto mechanic for 49 years and have never had a problem, until now that i coundn't solve. Could it be the exhaust has a problem causing the cylinder to overheat?

 

Welcome to the forums.
It sounds like the CDI could be heating up. (like the old condensers would do on cars)
The pipe could be plugged.
Maybe the fuel tank vent is plugged.
Let's go from there.

 

I've checked the tank vent. I also checked for spark when hot and it seemed ok. I disconnected the exhaust and it seemed to run ok. I blew through the exhaust and there wasn't any restriction, but with it disconnected it ran without stalling, but didn't seem to have as much power. I'm thinking it needs the back pressure to run properly. Thanks

 

Fixed ???
Just wondering , seams to be a plague with this little quads. Dealing with similar issues.