it sounds like it is seizing up to me. two strokes will smoke a lot anyway just because they are burning oil and they are, well, two strokes. what oil percentage are you running? you should use around 20% on those two strokes. The reason i think it may be seizing up is when the temp gets too high, without warning, the tolorances of the sleeve get so close that it clamps down on the piston and causes it to stop running. try going to a higher oil percentage. keep in mind, if it is seizing up it will eventually ruin the engine.