I have an lt 125 that runs like crap, and the engine backfires through the airbox. what could cause this?

 

I'm not an expert mechanic,but a lot of the time the carburator is the problem. If the jetting is wrong it could do this. You could also have a problem with the ignition timing. Just a couple of things to think about. I would try cleaning the carb first. When taking out the jets, turn the jets in clockwise first and count how many turns in so you can back them out to the same setting when you put it back together.

 

well i had a problem with my ds650 just recently and took it apart and this is what i found my quad had been backfiring due to the head pipes not sitting right and I needed to order new gaskets and get new studs and nuts so the head pipes would sit right but it could also be a gasket problem for you. It was backfiring because when at high rpms it was sucking in cold air into the hot engine and would cause a vacuum and would just backfire. Check your plugs also and see what color they are.