As far as I know you cannot deactivate it. Its pressed onto the exhaust cam. Your manual will give you a spec. It will probably be low because of the automatic decomp, but spec shows 77 - 124 p.s.i. You should really do your test with the bike cold. After you get your reading, pour a few small drops of oil in the spark plug hole and retest. If your compression goes up, your piston rings are wearing. A better test yet is the leakdown tester. I am a motorcycle tech by trade, so I hope you find this helpful.