yea i kno its a stupid question. but which spark plug do i take out to check the compression, leading or trailing? and what should the reading be for good compression?

 

Trailing (top)...

Should have at least 85 psi, each face, each rotor, per the book. Personally I think anything below 90 is bad...

 

i've heard from some people on the forum saying that the "piston" compression tester is not suited for rotary engines, but the rotary compression tester is like 100+ dollars... is this true or do all of you use piston compression testers anyways?