I took a look at the butterfly, and the screw that holds it to the shaft had come loose. I tightened it up with some red locktite so we'll see if that was the problem.

It's amazing how things come apart on these paint-shaker motors. One time I found that the whole cylinder had come loose from the crankcase. You have to check and locktite everything on a regular basis or it just shakes apart.

Thanks,

Mark