my dad and I are doing a compression test do we put the tester in the top plug or lower plug?

 

I'm just throwing something out here. I've done a lot of compression tests, but none on rotaries. However from my understanding, it shouldn't matter, they both feel the same compression. I'd just make sure and remember that all plug wires are off. Hope it helps

 

Compression was just done. We got about 80 psi in the front and rear we got 75-80 psi. We did a home brew test on the rear too all the gusts of wind seemed equal. So i guess im in need for a rebuild soon.

 

Id use the lower plugs. The trailing (top) hole is really small.

 

Amazingly enough the Mazda instructions say to use the top (Trailing) hole!

It surprised me because the opening into the chamber is small and typically everything else (such as initial timing) is done off the leading plugs. They *are* power-making first-firing plugs after all.

So use the top ones.

If you remove the valve from the bottom of the tester (or hold the release valve down if yours is like mine) then you can actually observe the "even-ness" of the pressure between each chamber by watching the needle bounce. It's a bit more accurate than just listening.

80psi is okay, not "it's gonna die" but not "it's a new engine" either

Jon

 

We did that too some how the guage broke so the needle bounced per rotor face. THey were all even bounces..

 

Mazda factory specs for compression is 85lb. Are you having issues to make you think you need a rebuild?

 

no its starting good but a while ago it was having issues. and was flooding.. but the problem is going away. Are the specs really 85psi? i thought it was like 110psi or something.

 

90 and up is great.... below 90 and no lower than 80 is ok. under that is low.