Did u remove the schrader valve from the compression tester? If you didn't, the only thing that test is good for is showing CUMULATIVE compression on a rotor housing (all three faces combined) this bumper should be above 100 psi ideally, but cam be as low as 80 on an ok engine. To properly test compression between rotor faces you need to remove the schrader valve in the comprehension tester and observe the bounces. They should be much higher than 40-50. (My motor is around 90psi/ face w/ 140k). Also make sure the gas pedal (throttle plate) is fully open while cranking and that the starter is spinning the motor fast enough (iirc 500 or so rpm) all these things can affect results. As pointed out earlier, even pulses are more important than specific numbers (especially if the motor runs ok) as all the aforementioned items can affect results. More than likely its that poorly adjusted bullshit carb setup that's causing your problem.