Compression probs

[MicahShane]

Howdy folks, new to the group and the GS world and looking for some wisdom.

I bought a 1977 GS550 that a guy had done all the hard work: polished the cylinders, painted the frame, chopped the frame for a custom seat, painted the tank, etc. After a few months, I noticed an oil leak. Long story short, I had to nurse it home one day and it's been sitting til I had time and space to get into it. Oil appears to be coming out around the valve cover. Potentially the head gasket as well.

This past weekend I did a compression test on the 4 cylinders. Since the bike is not running now, I couldn't warm the engine so I know the numbers might be a little low. However one cylinder didn't even read. Any thoughts on why that would be?

Readings:
1: 90psi
2: ~
3: 100psi
4: 90psi

'Preciate any thoughts or advice on next steps.
- Micah

[eil]

Those numbers are fine. The #2 cylinder might just have a little carbon or something preventing one of the valves from fully closing. You can try putting a tablespoon of oil or so in through the spark plug to see if it improves. But chances are if it was running before, it'll run again.

How much oil are we talking about? If it's just a little bit, clean up the engine as best you can, run it for a bit (not long, remember: air cooled), and see where the oil is coming from. Then replace that gasket. Since the bike is new to you, you shouldn't trust any of the previous owner's work. Get it caught up on all regular maintenance. That includes checking the valve clearances, which will require a new valve cover gasket at a minimum. See the mega-welcome link in my signature that will get you pointed in the right direction.

Welcome!