rotaryrascal

Can you do a compression check a rotary? if so, how?

DJ Rotor

Yes, just use a regular compression tester with the schrader valve removed. As you crank the engine, the needle will bounce as the compression strokes go by. You should be looking for even, strong bouncing, up to ~100psi on the gauge (the exact number is not quite so important as the evenness). If you have one strong bounce and two weak ones, you have a blown apex seal. A really good way to do this is with a video camera recording the meter - then you can play it back in slow motion to see more clearly what the readings are. You can also do a cumulative test, with the valve in place; the needle should jump up to ~100psi with the first compression stroke, then slowly work its way up to ~125psi.



Of course you want the ignition disabled while you are doing this.



(this should really be in the faq...)



J

rotaryrascal

ok, thanks