Changed the oil in my K75RT last winter.  Filled so that after a bit of running the level was about 3-4mm below the top of the circle on the sight glass, figuring it would drop from there.

Took the bike out and put 110 miles on it a couple weeks ago. It ran well and appears to have normal fuel mileage.  Was working on the bike this evening and noticed that the oil level is now touching the top of the circle on the sight glass.  There doesn't appear to be any milkiness indicating water so I am thinking I may be getting fuel in the crankcase.

Anyone know how that might be happening?  And where to look for the source?  All I can come up with is an injector that isn't sealing off completely and allowing some of the pressurized fuel in the rail to leak into the intake port.  But how does it get from there to the oil if the intake valve isn't open?  I could see it on an old engine with a mechanical fuel pump having a diaphragm leak.  But on these engines the fuel and oil are pretty well isolated, aren't they?

Is it possible that I just had a bubble in the sight glass?

Was it on level ground both times?

Did you use the centre stand both times?

If fuel is getting in there you should be able to smell it, or drain a bit and see if it burns.

I have found it takes a very small difference in angle of the bike to make the level in the sight glass change. I think this is because the sump doesn't sit central on the bike it is offset to the left and so if the bike is leaning a bit more to the right than when last checked it can appear that the level has increased quite a bit. Also once the oil level gets to the centre of the sight glass the same volume of oil added has a bigger effect on the level than it has at the lower part of the sight glass because internal components start to be immersed.
I ever only fill to the centre of the sight glass because of the parking on the sidestand and smoking the whole district out problem. The bricks do it even though the factory pinned the rings, my K1100 is very good at it.

To answer the question of the stand and parking.  My bike has sat in the same spot in my garage on a concrete floor.  I always park it on the centerstand and this is where I check the oil.  The only difference I can think of is that since changing the oil I replaced the original K75 centerstand with the straight leg K1100 centerstand to make it easier on my back to get it up on the stand when I park.

The stands may be different, but the height of the rear wheel looks very similar, so I don't think the geometry of the parked bike has been substantially changed.

I think I will be taking a bit of oil out tomorrow.  I am interested in how much it actually takes to raise the level that amount, and I want to see if I can smell any gas in the oil.

As far as my question, I an hoping someone else has seen this and has an idea of how the gas if any is getting in there.  Or if indeed it's possible to have an air bubble in the sight glass that causes it to read low initially after an oil change.

In any event a little oil is coming out tomorrow and I will be reporting what it smells like.

If the inlet is open and the exhaust closed it will leak past the rings.
Be glad it isn't like my Z1300 Kawasaki, if the fuel is left on and a needle and seat in LH carb leaks it fills the crank cases then up the breather into the air filter then out onto the ground and with a full cylinder a conrod will bend when you try to start it.  I think every owner has had all but the bent rod happen a few times before you remember to turn the fuel off.

Exactly what happens to my tractor when it's parked.  Fortunately, the starter isn't strong enough to damage anything.  It just locks at tdc.  Have a fuel shut off on it now.

Point-Seven-five wrote:to make it easier on my back to get it up on the stand when I park.


I think I will be taking a bit of oil out tomorrow.  I am interested in how much it actually takes to raise the level that amount, and I want to see if I can smell any gas in the oil.

Or if indeed it's possible to have an air bubble in the sight glass that causes it to read low initially after an oil change.

In any event a little oil is coming out tomorrow and I will be reporting what it smells like.

I have an 1100 and a 100 and the 100 is way easier to get on the centre stand. Just my opinion. I believe technique plays a greater part than any stand configuration.

It is not possible to have an air bubble. Behind the sight glass is a backing plate (probably to give a reflection or reference point or some crap) and it is open on the top, sides and back (holes drilled).

It takes very little oil to go from 'almost there' to 'crap, overfilled' when looking through the glass.

How fuel would get in there? No idea.

Good luck getting "a little oil" out. Loosen sump drain plug.... a bit more....a bit more.... just one mo....crap it is in the pan and all the oil is coming out...put a finger on it... where is the...may as well do an oil change now.

Maybe the long weekend and beer is making this funnier in my head, but it sure beats watching football

Rossko,

What sort of coffee are you drinking there? It's not Irish coffee is it?

Point-Seven-five wrote:The only difference I can think of is that since changing the oil I replaced the original K75 centerstand with the straight leg K1100 centerstand to make it easier on my back to get it up on the stand when I park.

The stands may be different, but the height of the rear wheel looks very similar, so I don't think the geometry of the parked bike has been substantially changed.

.75,

I also changed my centre stand to the straight leg version last year (June 2014):

https://www.k100-forum.com/t8174-centre-stand#95612

As detailed in the post at the time, my increased difficulty in getting the bike up onto the centre stand was due to lack of grease and badly worn bushes (note to self....go and get grease gun on those centre stand nipples and give em a good squirt of grease again...today! Post-note to self: Bushes now greased on side and centre stand, job done!)

I didn't notice any change in oil level...but I wasn't looking. I tend to keep my oil level at the top of the sight glass (with bike on level ground and on centre stand), topping up as required between oil changes. However, I have noticed that the ground clearance between the rear tyre and the ground has reduced a little (about 2 - 5 mm). Not that I measured it before and after, it's just that the rear tyre is now only just clear of the ground, whereas before it was sitting noticeably higher. This suggests that there is a slight difference in the way the bike sits between the two types of centre stand. I haven't a clue what the geometry of the internals of the engine oil chambers is like, but think it is entirely reasonable that even the slight changed induced by changing the centre stand is enough to give you a small change in oil level in the sight glass.

To be getting significant amounts of fuel into the oil sump would mean both your injectors and piston rings (and even your timing/spark plugs) are behaving badly and you will be able to smell the fuel when you do your oil change. Personally, I think this is unlikely. Likewise, if it is water causing the level rise - you will see emulsification of the oil.

My money would be on the side stand differences - do your oil change, reset your oil level in the sight glass and monitor to see if it remains steady (or very slowly drops with use).

First, regarding centerstands.  I have both a 4v 100RS and a K75.  It wasn't until I got the RS that I saw how it is a bit easier to get the bike up on the newer stand.  Can't attribute it to grease as I had both lubricated.  I suspect it has to do with the geometry of the contact point and how much the bike is being lifted as the stand is deployed.  I agree that the clearance below the rear wheel looks to be slightly less.  At the weight of these beasts, even a few mm less lift can be felt in my back.

Hoping not to have to do a complete dump of the oil as what's in there now only has about 110 miles on it and is essentially brand new.  It's too bad BMW had to baffle the filler so I couldn't use my dipstick oil change pump to bring the level down.  I know it's going to be messy, but I don't think I'll have to dump the lot of it.  Might only have to put in a few ounces to get the level right.

Not going to spend too much time on it.  Today is forecast to be sunny and warm for the first time this year.  I going for a ride!

Minimum level (bottom of the ring)
Maximum level (top of the ring)

Capacities between Min/Max approx. 0.6 litres (1.05 pints)

From the riders handbook
This might be of some help

The last several years or more BMW have been recommending oil level consistently be checked on an engine that's been running a few minutes, switched off and level, such as on the main stand when so fitted, due to the appearance of fluctuating oil levels.

I too have experienced fluctuating oil levels.  I've changed oil, run the bike some considerable distance and, upon rechecking the level thought the engine was consuming a bit of oil.  Next day the level was back up to where it had previously been. 
I just love a machine with character!

My '87 RS has always done that, so I never fill it more than a smidgen above the oil sight glass' bottom. Afterall, there are 3.something litres in it at that level, and the level will be at the middle a day or two later.

A longtime BMW mechanic I worked with years ago, and who favoured K's (he had an '85 with over 200,000 miles on it fifteen years ago), once told me "There's a lot of places for oil to hide inside that lump of a motor".

Sounds like 4-5mm changes are no big deal.  Is that right?

If it keeps producing oil then store it in big barrels and wait for the price to get to $110 then sell and flood the market

I'd expect if you put the original stand back on the oil would return to the same place it was when first put in.