Sorry to hear about your problems, this is most unusual.
So far all things mentioned have been positively ruled out? Its a simple 2-stroke so not much is left before going back and looking twice. I'll take a shot and say its a small leak the leak down test did not show. A very small amount of coolant or trans oil being drawn into the cases. Base gasket, case gasket, head oring, casting porosity. If its something rare like that then I agree I would want at least a new motor.
A quick but crude test might be to temporarily replace the coolant with a waterless type, or straight polypro glycol like Sierra (cheaper). The system pressure will be very little due to the high boiling point, so if there is a small coolant leak things should improve as less coolant will be forced into the cases. While not a definative test it might point you in the right direction.
|