oil level unreadable K75C 1986 new to me

[tcroullier]

Good morining. This topic is not new after researching it in this great forum. my oil level is not readable even with in tense light.1000 miles ago I did an oil change with the exact required amount and changed the oil filter. Of course I read on center stand flat surface. All I see is darkness, a red dot and circle. A few questions.
1) on my airhead it is not a problem to have too much oil. The old lady will naturally dispose of the excess. for that machine what is the downside of too much oi?
2) if I wanted to replace the oil level window, do I need to drop the oil pan or can it be done from the outside?

 I am planning a long trip to the Barber's vintage festival in AL. I will do an oil change with the required oil quantity again to be sure.

Thank you!

[tcroullier]

I just saw Snowbum's procedure with a heated screw driver so 2) is answered! https://bmwmotorcycletech.info/sightglass.htm

[daveson]

The sight glass might not need to be replaced, it might just need a clean, or the silver plate behind it might need cleaning also. If not for the silver plate behind the glass, you would only see into a black sump.

After removing the oil filter cover and the oil filter, you will have access to clean them from the inside.


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[Ingo]

Put her on the side stand and see what you see. It should show low or nothing if sight glass is just covered due to high oil level.
 Otherwise, yes, sight glass replacement happens from outside. It's just a plastic disc with seal.
 The "reflector" behind it is somewhat important,  though....

[Laitch]

. . . sight glass replacement happens from outside. It's just a plastic disc with seal.

To clarify, the sight glass is composed of a sealed ring surrounding a clear plastic lens in the front and a silver perforated disc (indicated by arrows) in the rear. Oil enters into the space between the lens and the disc corresponding to the acceptable oil level in the sump.

Cleaning from within the sump would seem to require flooding the space between the lens and the disc with solvent through the holes in the disc until both surfaces are clear. Scrubbing would require careful use of a brush or sponge mounted securely on a thin flexible wire.

[tcroullier]

thank you all. for all the responses. I am in debt! I leaned the bike to the left and saw that I have too much oil and also that the silver disk is now yellow, making it hard to see anything. I rode her 500 km this morning with no real issue so I will keep her as is for now.

[daveson]

The oil level shouldn't be above maximum, it could result in excessive sloshing and excessive air bubbles in the oil, reducing the amount of lubrication required. If you put in the correct amount of oil, the level might now be above maximum due to contamination, for example fuel or coolant might be getting into the sump oil, obviously that wouldn't be good, that would also result in the lubrication being sub par.

[TriSpark]

Replacement oil sight glass assemblies are still available new, the one on my 1987 K75 had similar aging issues to yours when I got it, but not as bad, so I just replaced it from the outside and solved the issue.

[Laitch]

I leaned the bike to the left and saw that I have too much oil and also that the silver disk is now yellow, making it hard to see anything.

Accurate assessment of oil level is done with the Brick level, not leaning, and the most accurate reading is taken when the engine is turned off and cooled slightly after a run.

[daveson]

Ok you can see the level but it's difficult. There's probably an easier way to clean it.

Most engine oils for cars have an S rating, so are suitable for petrol engines, but some also if have a C rating so they're also suitable for diesel engines. Oils suitable for diesel engines have more cleaning additives, that might be enough to clean up the sight glass. It probably also helps to prevent the sprag clutch from clogging up. One example is Castrol GTX, this normally has both ratings.

[Ingo]

Accurate assessment of oil level is done with the Brick level, not leaning, and the most accurate reading is taken when the engine is turned off and cooled slightly after a run.

That is assumed to be understood.  Sidestand is to confirm it's  just overfilled. Normal oil level on sidestand shows an empty sight glass, at least on my K1100...
The reading when parked level was indicated in the first post. And I don't think the oil level is all that critical as long as we're  between min & max.
Also: oil change is done after engine has been run and is at temperature.  Cold oil doesn't flow as well and leaves sludge in the oil pan, probably leading to overkill and still (again) dirty oil....