This weekend, I tore apart the engine in my '79 KZ650 SR because my compression was low (50-70 psi across all 4 cylinders with a slightly warm engine test). I replaced the head gasket and all the piston rings. I checked to make sure the valves weren't leaking. I put it all back together tonight and checked the compression. Essentially no change. It's still about 50-70 across the board, and I'm about ready to pull my hair out.
I tested each cylinder while cold (haven't run the bike in several weeks) with the other spark plugs in because I didn't know that it could make a difference. The carbs are off with only the intake boots attached. The exhaust is also off because I had it up on a motorcycle jack to work on it.
I'm planning on putting a little oil in each cylinder tomorrow and running the bike for a bit before I test it again because I've read that those can both make a difference. But I feel like those things adding almost 100psi is a longshot.
Is that low of a reading normal for a cold engine? I need all the help I can get. Thanks guys!
Engine needs to be at operating temperature, remove all 4 plugs, disconnect power to the coils and spin over for ten seconds on each cylinder with wide open throttle, you will then get a true reading, but before you do this put a few miles on it at various engine speeds to bed the rings in again.