Anyone out there have a cylinder compression figure for their 850? Mine seems low (to me at least) at 120 psi. I'd like to know anyone else's compression figures to know whether I should strip down engine to replace piston rings. Oil consumption is high on my vehicle so I'm
starting to fear the worst...
Fred Russell

More important than the compression, is the variation. And in my experience, it's not just from one test that any conclusion should be made, but from tens of thousands of miles of records always done with the engine in the same state of tune.

If your engine has just begun to use oil, the question is how much the compression on the offending cylinder(s) has changed. The other thing to do is to perform a leak down test before you disassemble so you know where to look.

Often my advice is to run the engine hard for a while, and road draft it if needed so you don't foul your plugs. Sometimes running the crap out of it will loosen the rings up and fix it. (This is sometimes called an "Italian Tune-up"). Other times it will break it, but what have you got to lose?! If you have worn bores and pistons (very common on 850s), you would need to bore it anyway.