First some background.
I've got a 1982 KZ1100 A2 which I don't know much about its history. I got it last winter with 30,000 miles on it from my brother. He only had it one summer and didn't ride it much. He changed the oil but never the filter because the oil filter bolt was buggered to the point where it couldn't be changed. It also leaked oil from the oil pressure sending unit (where the oil cooler lines go, too). So he didn't have any reason to suspect it burned oil (be probably just assumed it leaked out).
First thing I did was check the compression - and got readings at 130,132,130,145 (cold, no valve adjust). At the time I didn't have a manual and it didn't billow smoke and it ran/started pretty good. It had a lot of power so I figured it can't be THAT broken so I assumed all was well and set to overhauling the rest of the bike (forks, battery, shocks, seat, tank, mufflers, carbs, oil leaks, etc).
I also measured and adjusted the valves, fixed the filter bolt and changed the oil. At this point I started riding the bike more and noticed that it burns about a quart of oil every 750 miles. At first I chalked it up to hot weather, but the next 750 miles in cooler weather it burned oil too. So changed to a mobil 1 redcap, thinking a) synthetic = more uniform molecules = less small molecules getting past piston rings, and b) thicker (15w50) weight = less getting past piston rings. It made no difference.
So now I have a shop manual and see that the compression readings should be in the 152-181 range and reading this site I know the valves must be adjusted and the engine warm and WOT when taking readings. So I did that, and get 150,138,138,150 with all the spark plugs out. Ok.. I have two iffy cylinders, but am surprised how different the readings were from the first time, but chalked it up to the valve adjustment.
Then I read about putting oil in the cylinders to see if it is the rings or guides, but this time I did it cold as I read there's about a 10psi difference. Before oil added and engine cold and only one spark plug removed (the cylinder I'm reading) I get 150,150,150,150. Huh? I'm thinking with the other three plugs in it is pulling more air through the airbox (maybe I should remove the air filter? It is fresh). I put oil in the two outside cylinders and it jumps up to about 200psi (I haven't found a good clean easy way to get oil into the middle two without taking the tank off yet).
So here's what I'm thinking:
The piston rings are worn but seem to have enough compression for the engine to run strong. The compression is on the low end, but not really far out of whack. So why am I burning so much oil? (there is no leak).
Post edited by: c_aasland, at: 2006/06/28 10:14