Since respraying my bike the fuel cap did not close square to the line of the tank so I decided to see if I could 'unpin' it and reset it.
I had previously posted in the 'stuck fuel cap' thread that I had a vague memory of driving a pin through the threaded section of the cap. I did say it was 20 years ago and I now know exactly how I fixed it and I don't think anyone else has described this method before.
I popped the top part of the cap off the lower part, it is a press fit and comes off pretty easily. The lock barrel and a spring will then drop out.
It seem tthat the reason the caps spin and can't be unscrewed is that the small square black plastic locking piece stops being engaged by the small spring behind it.
What I did 20 years ago was to drive a screw through the plastic lock barrel in line with the broken spring. The right size screw does 2 things, it pushes the black plastic locking piece back to where it should be (permanently) and becomes another locking tab that engages on the opposite side.
Put it all back together and I can guarantee that this will work for another 20 years.
I replaced the rusty screw with a new one and put the whole lot back a quarter turn from where it was and now my cap still works and it lines up across my tank.
Hopefully the attached photos will make all that talk clear for you.
If you have a cap that you can't unscrew from your tank because it is free-wheeling just carefully lever the top off and you should be able to remove the rest of it with a suitable width piece of steel or a file even.
The top 2 photos show the lock barrel and the old screw undone, the screw needs to be screwed all the way in. The last photo shows it about to go back together with a shiny new screw head on the right.
This is a 1984 fuel cap without the BMW logo, the early ones could be different.
Bruce
