TOPIC:

Hey guys, I've got a 1978 KZ400 b and it's burning a bit of oil. There are no stains or visible leaks, so it must be burning it. A compression test shows that it is right on spec at 156 psi in both cylinders. So it's not the piston rings... What else could it be?

The big ways the engine will burn a lot of oil is via a ring issue or leaky valve guide seals. If you're sure the rings aren't a problem, it's probably the seals. Although, the head must come off to service either of these, so it wouldn't hurt to replace the rings while you're in there anyway.

I'm pretty sure you can have oil-consumption from the rings and still have strong compression because you have two compression rings and the oil control ring, and the second is responsible for minimizing oil consumption.

You can have great compression and still have bad / worn oil control rings.

I would suspect the valve stem seals or a gummed up oil control ring. Running a few ounces of MMO in the gas tank for a few fill ups can help free up the rings if they are indeed sticking.