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I picked up a new headlight gasket for my friends '78 R100RT project and I'm not sure how it gets mounted. One of my bikes has it between the lens and the reflector and the other it's between the headlight assembly and the bezel. Any clues as to where it belongs and correct orientation the ridges?

Between lens and reflector. Its job is to keep the inside of the reflector clean.

Edit:
You can clearly see it on the fiche.

It wraps around the lens with the ribbed side out to provide a water seal.

Thanks!

Wow, I got lucky. This thread is right on time for me.

I have a new gasket for my headlight on a 1977 R100/7. The old gasket appeared to be flat, sandwiched between the lens and reflector, and sealed with clear silicone. There was only a very thin line of gasket visible around the circumference of the lens/reflector assembly. I used a razor blade to slice the lens from the reflector. An autopsy on the old gasket revealed no trace of sealing ribs. I'm the original owner, and I know this is the first time the headlight assembly has been opened.

My questions are:

Did BMW change their gasket design since 1977?

Is the new gasket used without silicone?

If so, is the lens held in place solely by the spring clips and the chrome bezel?

Some have posted they tape the lens to the reflector. How does the glue on the tape hold up to the heat of the halogen bulb?

It wraps around the lens with the ribbed side out to provide a water seal.

Once on the outside, are the ribs facing to the front or rear of the lens? I can get it to fit in either orientation, neither of which has a clean fit in the reflector. Should I just assemble everything and depend on spring pressure to force the gasket into place?

Just wanted to add to the database of knowledge.

I called Bench Mark Works, and a guy (Richard?) was nice enough to search their inventory for a NOS lens with factory-installed gasket.

The two ridges shown in Tim's photo go towards the rear of the assembly, sealing against the reflector. Seems like I'm going to need some extra fingers to hold all the pieces together while installing the clips.

No, it is easy. Use 5 clips. I have done hundreds by myself. The original clips are not good spring steel and can get bent easily. Then they don't hold well. They can be bent back into shape, but I never had much confidence in doing that.