hello all, i just recently purchased an 87 trx250x. The guy i bought it from said it had a bent valve. I took the motor apart and replaced that valve and all the valve seals, put a whole new top end gasket kit on, cleaned the carb out, new spark plug, drained all the old oil and gas out, put brand new fluids in and threw it all back together. It doesnt want to idle, rough/hard to start, blows non stop white smoke, and it backfires out of the carb. i cant seem to figure out whats wrong with it, Does anybody know why it does this?