Picked up a beater shee for a few bucks. Went to check compression but gauge wont hold psi. When I kick it jumps to 30, then immediately falls. I kick again ... Same thing. Is it a bad compression gauge ( cheap gauge ) or could it be motor problems. Thanks for your time. I did the thumb test and both cylinders feel ok but thumb test doesn't tell much. My hand is not on the pressure release either.