Is there any special way of doing it on rotory motors? Doing it the conventional way says our motor is within 5 lbs of stock... think that shows it has some pretty good life left? Or is the conventional way of doing a compression test not accurate?

Thanks
Chuck

 

You will have three compression pulses per rotor, as each apex of the rotor passes thru the combustion chamber area. You need to be able to measure each of these pulses: (three per rotor x 2 rotors = six compression readings) to compare to each other. You can use the mazda specialty tool, which measures and records each pulse. Or- you can remove the one way valve from a conventional compression tester and have someone crank the motor while you watch the gauge readout like a hawk. The readings will go up and down real fast, so you will need to watch carefully. As in piston engines, the significance of the readings is not just the maximum compression, but the comparison of the readings to each other. One reading which is significantly lower usually means trouble. If all of your readings are within 5 psi of stock, barring any other problems, sounds like you have a healthy engine.

 

when you get results they either are good (left rotor) or bad (right rotor) like the pic i have here

 

Ouch!