K series compression test with ACR?
 

the K series Kohlers have an automatic compression relief feature. How does that affect a compression test and what psi value would you like to see? I tried to do one with my 149 project engine (which seems to start and run fine) but I only get about 50 psi on the compression gauge. I went over to my 108 and tried to do a compression test and got zero. That engine was just overhauled, starts and runs great. What gives?

As you know the ACR holds the valve open a bit, how much is dependent upon a lot of factors.
So a compression test is a mute point, unless one goes to the trouble to disable the ACR for the test.

How hard is it to disable the ACR? Is this something that can be found in the service manual? I'd be interested in figuring this out as well.

I think the manual says to spin the engine backwards to get a compression test. You have to use a rope to pull the engine. But with an ARC a good # would be about 50 psi rotation with the sg.

My 125 manual says the ACR turns off about 650 RPM.

I looked again at the service manual and it mentions that it is not practical to do a conventional compression test on the engine due to the ACR. They recommend a visual inspection of the cylinder and valves.