From:Ronnie Tanner
Subject:RE: Compression Date:Wed Aug 14 22:29:12 2013
Response to:18715
Ryan,I checked my 165 service manual for a compression psi specification and could not find one listed. The compression ratio listed for the 165 is 6.6 to 1 which is a low ratio. 75psi sounds low to me but I can't say for sure. I've never checked the psi on my 165. Having the carb and muffler unhooked should not affect your compression psi.
You said you did a dry compression test. Pull the sparkplug, add about a half teaspoon of 2 stroke oil, reinstall the plug and repeat the test. I would expect the psi to be in the 125psi or higher range.

Some of the old heads on here should be able to chime in here and give you an exact number to look for.

I did a dry compression test on my 1953 165cc. It was about 75 psi. Is this normal for older motors? Also, I did not have muffler or carb hooked up to motor. Not sure if that matters.