If your sitting still and shift up into 2nd you can feel it go into gear. Then if you sit for a few seconds and let the clutch out it pops out of gear. If you slip the clutch and keep pressure on it it will stay in gear. It also did it in 3rd when my son shifted up it popped right out. Only happens occationally. Took the cover off and all looks good and shifted threw the gears nice and smooth. I had the tranny apart not too long ago and all looked normal. This started a few rides after that. Any ideas...thanks