I have a lot of trouble with the vibration on these little engines. I have removed the crank and checked them for balance, just on a jig. The crank is heavy with extra weight added to the flywheel sides. The extra weights are removable and are hollow in the area near the pin, this is how they get any balance. The hollow spots are cast in so, I fear it is not accurate. It would be fun to see if there is another crank that would fit, A Hodaka? I am curious, did the extra motor mount help? Have fun, Dave