i was riding at a local track today and i havent been to this one yet so i was taking it easy getting a feel for it and going up a small jump i rode easy over it and the bike just quits. i couldnt get it started again until i took it to a big hill and rolled it down and even then it was really hard to do as i had to be at least 1/2 throttle for it to start and when i let go of the throttle for a sec it quits and a puff of smoke comes out of the left side of the engine. i knew it was oil by the way it smelled. and i sit it on concrete for about 30 mins and i saw no drop of oil so i dont think its leaking. it still kicks over so i dont think there is anything wrong with the piston or crank. i think its the valves. im tearing it down tomorrow to see what it is but i want to see if yall know what may be the culprit. oh and btw when i first got the bike to the track i started it up 1st kick and had the choke on and while it was warming up i was getting gear on and when i turn the choke off it died. so i had to push start it but after i did that it idled fine. i think its valves but i dont know nearly as much as most people on this site.