Low hr M20 issue

[OldSkull]

After "swapping" this low hr M20 in my 1872 (Now 2072), I found out really quick, it's not going be a turn key swap. The carburetor got issues, some sludge where hiding behind those shield but no oil leak from both crank oil seal and head gasket. I clean the engine put it back together and in the 1972 he goes.

I decided to do some tuning and testing, I manage to make it run smoother but the carb still need to be restore. no big deal since the M18 got one running well I swap that later if need. Things get wear when I did a compression test here the result after 10 minutes warm up.

First test cylinder one 105psi

First test cylinder two 75psi


I warm up the engine again and give it another try:

Second test cylinder one 95psi (sorry this one is out of focus)

Second test cylinder two 89psi


I think it's a bit low for a 200hr engine, I suspect a valves leak so as soon I found out how to find the dead center position on this engine I will do a leak test. If my suspicion are right I need to remove that engine from the cub and open it, This need to wait a bit... story to followed soon...