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My bike (1977 R100RS) has a clear oil level inspection pug below the filler plug on the final drive.

Anybody know the part number for this? Can't see it on the parts fiche.

I think that it was fitted by previous owner. The 70s bikes did not have level plugs, you just filled to the bottom of the filler plug.

R100SRS wrote:My bike (1977 R100RS) has a clear oil level inspection pug below the filler plug on the final drive.

Anybody know the part number for this? Can't see it on the parts fiche.

Final drive with a sight-glass? Can you post a pic?

Here is a picture of the item.

Looking at it again - it might just be a blanking plug rather than an oil inspection plug. I presumed that time had faded the plastic to an opaque off-white.

I'm willing to bet its where the drum brake shaft went through and when BMW changed to rear disk brakes it had to run out all the old drive hubs and find a way to plug the hole.

The part number might be: 33111236826

I doubt if BMW ever made a separate casting for the disk-brake models, but the rest of your logic sounds...sound.

And besides, the oil level in the final drive would most likely be below the bottom of that "sight glass". So, it would do a lousy job...if it were a sight glass.

Kurt in S.A.

I would guess that previous owner made the mistake of retrofitting disc brake to his drum braked bike?

Worth checking to see if you have the correct RS gear ratio stamped on the bevel drive unit and check realoem with the frame no to see what bike it is recorded under. Do you have 40mm or 38mm diameter exhaust pipes?

40mm exhausts.

Drive has 33/11 stamped on top.

Compression is 155/160 psia.

Note: this bike was a BMW special order. Who knows what is what.

If it is a sight glass, it is in the wrong place. That would be way too much oil.