either valve seals or rings...also make sure your choke is off the whole way... i redid the topend of my father in laws beartracker and i went riding with him and it was smoking .. he said it has done it ever since i rebuilt it , and come to find the choke was pulled out one click ..pushed it in and it quit smoking
what color is the smoke? if it burns black then its getting too much gas and if its blue then it is burning oil. mine does the same, when i get on the gas or a long decelaration. im rebuilding it this week though
well its blue it prob needs a rebuild but cash is tight so were prob just gonna drive it till it blows then rebild it with je 10.5 ext prob 30 over or so