Hey guys, I just picked up a 1987 TRX 350 4x4 tonight, it's really nice, in really good shape, and I'm excited to get it on some local trails. It starts right up, and runs well, but there is a knocking noise while it's idling. As soon as I give it some throttle it goes away. It shifts great, and otherwise is perfect. Anyone have any thoughts on what it could be? I'm not all that mechanically inclined when it comes the motors, so I'm not sure if it's a valve adjustment issue or if it's a timing chain issue, or a cam chain (is that a thing?). Any help would be great!