I have a 91 Polaris Trail Boss (4x4) that I just recently put a new piston in. I bought it from a fellow who didn't know what he was doing and he broke a piston when he was trying to put a new one in. The compression is back up again with a new piston installed. Everything runs great, except it likes to bog down when you first warm up the engine. Its fine while its cold, and runs okay after getting the engine hot (maybe after about 25-30 min). It will also run okay if you keep the engine reved up high, but if you slow down to change to reverse, a sandy/rough spot, or let it idle for a bit, then it gets into this rut where it just sits and idles. It wont completely die, but it bogs out if you try to give it gas. I have found that if it gets into this bogging rut and I push the starter switch (with the engine running) it will snap out and start running as long as you don't let the rpm go to low. I'm afraid I'm ruining my starter though. Hopefully someone out there can help me with this. I tried to explain it as best I could. Thanks!