HI Just wanted to see what people think? I just did a compression test on my 1990 k100lt the results on the cylinders were 
1- 8.9 bar
2- 8.5 bar
3- 8.5 bar
4- 9 bar 
(Engine hot throttle open full) 
The resin why i did the compression test was due to oil consumption I know these engines use oil ect
but I worked out 0.4 of a litre on a 200 mile journey mostly motorway last weekend. 
Then i use it for commuting one day i spent a lot of time in traffic so 
it was running hot for most of the 30 miles or so and it used 0.3 of a litre (but it was a hard drive for any vehicle!). The only other thing to consider is it needs 
the flywheel oil seal doing but this only puts the odd drop of oil on the floor! same with the water/oil pump a rare drop on the floor! (no overheating ect) other wise the bike runs really well. Has anyone else had this sort of oil consumption? 
Love to know what the general consensus is? or do i have an other problem? i.e valve seals? thanks in advance K.

I would plan to fix the front and rear seals and see how it goes after that. I have seen the 16V engines use a lot of oil including my K1100, it was consistent loss until about 18 months ago when it suddenly started using a lot more so its been retired. Others I have seen go for a long time.
8V usually don't use a lot so just keep an eye on it. The smoke on start up can be bad sometimes but it doesn't seem to use much oil.

RicK G wrote:I would plan to fix the front and rear seals and see how it goes after that. I have seen the 16V engines use a lot of oil including my K1100, it was consistent loss until about 18 months ago when it suddenly started using a lot more so its been retired. Others I have seen go for a long time.
8V usually don't use a lot so just keep an eye on it. The smoke on start up can be bad sometimes but it doesn't seem to use much oil.

Hi Thanks for your reply, I still plan on keeping it so i will be starting on the rear main seal soon enough but I will just keep an eye on it and not do anything too drastic! K.

A compression test should always be done on a stone-cold engine. You're checking for leakage past the rings and the valve guides; when the engine is hot, these tolerances close up and give a false reading.

If you frequently use the side stand, the oil can collect in the cylinder head. When the bike starts up oil gets past the value and into the cylinders, being burned off.

Sometimes these bikes like to "hide" oil so if it seems to burn a lot on one trip it may be an anomaly so I wouldn't be as overly concerned as if it were consistently burning a lot of oil.  Even then, what are you going too do about it? Given the effort and expense required to do a teardown and rebuild it makes more sense just to swap in a used engine given the number of them available and relatively low cost.

And, from a pragmatic perspective, even if it does burn more oil than usual it's not something that is prohibitively expensive, it just means you need to keep a closer eye on the sight glass.

Then again, if it's really losing compression to the point of killing your mileage or noticeably degrading performance then it's time to part the bike or swap in a "new" motor.

JM02, YMMV.

Often an engine will be constantly using a small amount of oil but with short trips and round town running the oil loss is covered by a very small amount of fuel that gets past the rings, so it looks like it is not using any oil. Then comes a long run of a few hundred miles or so and the fuel evaporates and it looks like a heap of oil has been used so you top it up and it doesn't use any more.
I remember a car I had used almost a whole litre in the first part of a trip and not a drop more in the rest of the trip. It will be more likely to happen in cold whether when warm up takes longer and oil temperature isn't as high on the short runs around town.

I have a 16V K100 that uses about the same amount of oil as yours(1.0L/900 miles).  Compression is good in all cylinders(~9.5 bar).  Engine has about 125K miles, runs smooth and strong, and starts readily.  Smokes when cold, but stops when warmed up.  I seldom park on the side stand, and oil consumption is consistant under all riding conditions.

I have replaced the valves stem seals, head gasket, rear main seal and the clutch o-ring with minimal improvement.  When I pulled the head for the valve stem seals I checked the cylinders and they showed no signs of wear. 

I suspect(hope, really) that I may have stuck oil control rings in the #1 and #3 cylinders.  I am now running Marvel Mystery Oil in the fuel and crankcase with the hope of loosening them up.  If it doesn't work, I will probably just keep on living with the consumption.  With the price of parts to do a ring job on the engine around $450 I can buy enough oil to ride another 50,000 miles.

I have looked at replacing with a used engine, but for the work involved installing a short block, I could just as easily install a set of low mileage pistons and rings for about $65.

The allowable oil consumption spec from BMW is 1.5l/1,000km.

Thank you all for your input, I think i will just be keeping a close eye on the sight glass from now on and not panicking!, I will probably go ahead and repair the rear main seal as it will need the splines lubing anyway as god knows when that was last done. It drives fine hardly smokes even on start up (unless on side stand), anyway if something drastic happens i am sure i will be back on hear looking for help! Thanks again K. 

Hello all,
I’m looking at a 75k mile 1989 K100RS and the compression tests (cold, throttle closed) are all around the 9BAR mark. The engine running warm sounds sweet. The trouble is that COVID stops me going to see for real so these are videos. 
Any views? I thought it sounded ok. 
J

Compression tests should be done with the throttle wide open and at least warm.

Compression tests should be done with the plugs out as well. Ground the plug leads to prevent coil damage.

9 bar with a closed throttle sounds okay to me. But, as has been pointed out, comp testing is done with a wide open throttle, all the plugs out and a good battery - this gives you the highest possible reading. The difference between cold engine (cold cranking pressure - CCP) and a warm engine is minimal on a k. Main thing is that the readings are close across all cylinders.