Chinese 110cc atv won't turn over
 

I have a 110cc Chinese (BMX) atv, in short the starter can't turn the engine over. I am getting power to the starter, starter spins when not connected to chain and starter sprocket. I put the atv in 3rd gear (3 speed w/reverse) and can turn the rear wheels, it does stop after a little turning but will turn again if you stop and try again....... I am stuck, not sure what the issue could be. Any help would be greatly appreciated