Fuel cap

[Big D]

I recently bought a 1978 100/7T which the previous owner had done alot of work on. It has a police gas tank on it and looks pretty sharp. The gas cap screws into it and is not a flip up. I stopped for gas the other day before a day trip and the cap would turn counterclockwise with a clicking sound but would not come off. Luckily I was close to home and went back and switched the /7 for my RT. Later, I finally got the cap off but it seems that the inner male threaded part of the cap will rotate free of the top part under load(thus the clicking sound). I do not have a key for the cap. I thought I would buy a new cap and looked at MAX's fische but cannot find a cap which has a long male threaded part in the diagrams. If someone who is familiar with the airheads could please help with any info, it would be appreciated.

D

[Paul Mihalka]

Later, 1979 to 1984, airhead gas tanks had screw-in gas caps that were flush with the top of the tank. Part no. I can find is 51252307168. The problem you have, the cap spinning, was well known. If I remember well, to get the cap off you drilled a hole through the cap where there is a small BMW emblem, stick a long bolt in it, and it came off. Lucky yours came off without extra work.

[Big D]

Thanks Paul. I'll check out the part number. When I look at the diagram in the parts catalog, I can't tell if the male screw in part is long like mine or that it is actually around the top of the perimeter of the cap.

 

D

[notacop]

What the guy said about drilling and putting in a bolt is good. I used a 4/40 screw which locked the mechanism so it would work. Once the little screw, about 3/4 to an inch long, was in place I forgot about it. I just checked my old R bikes. Neither have pins in them but I never use the key to lock/unlock them. I't a real hassle to have a empty tank an a faulty gas cap. Fine Master Race engineering!