Low compression after valve adjustment

.5 is a huge jump. Do you mean 0.05mm or 0.50mm?

It’s not normal to loose compression from a valve adjustment.  If it was good before the valve adjustment, then something is wrong.  You need to go back through and double check your specs.

Did you R&R the camshaft to do the valve shims?  Perhaps you've timed it wrong?


Perhaps you have too much shim and one valve is hanging open?
Pull off the exhaust and rotate the engine slowly through.  Do you hear air escaping on the compression stroke?
Do the same procedure with the intake.

Sometimes, a piece of rubber hose pushed into the exhaust or intake and held near your ear can help you hear stuff like that...  Works like a mechanic's stethoscope.

You should check it again cold. Valve clearances open up once you get the engine hot