Hey guys, wondering if you can help out a 2 stroke convert. I Just bought a 99 yz 400. I've been having trouble starting it and keeping it running. In the 3 weeks I've owned it I've gone through as many plugs. All blackened up (running too rich I assume). It will start with the choke on, but after it warms up, it will stall when you try to put the choke off. Has anyone seen this happen to them? I don't want to touch the carb untill I know what the hell I'm trying to do with it. Help!!!