[cayuse]

I'm just guessin' Alan. I've seen 2-strokes clap out after being run way too hot. Maybe a problem with rings, cylinder expansion, or head gasket leakage.

I don't share your experience on the GZ wrt to jerkiness when the engine is hot or cold. Mine is somewhat 'jerky' in the lower gears when transitioning from throttle closing to opening and vice versa. In higher gears, especially at lower speeds it is much smoother. I think it's due to the various inertias vs. engine compression.