Hi All,

I am not only new to the K bike world, but the motorcycle world as a whole! I got my K100 in a series of six laundry baskets from a craigslist ad. That was a couple months ago and now it is painted, powder coated and has had pretty much every rubber part replaced. 

The last system I am restoring is the fuel system and this gas cap has me confused. I ordered a standard rebuild kit but none of the rubber bits fit. I was told by an expert at EME that I have a "unicorn" gas cap that was only used on very early bikes. 



I haven't been able to find any other details on this cap. Have any of you come across it? Any information about why it exist or how to service it would be greatly appreciated.  I have a .zip file of pictures that I will try to post since I don't have the right to post yet.

Thanks,
Dan

http://forum.kforum-tech.com/members-upload/uploads/Photos_(14).zip

I believe the latter cap will fit and it is a better cap.
Regards Martin.

MartinW wrote:I believe the latter cap will fit and it is a better cap.
Regards Martin.

What he said. The early gas caps weren't too reliable which is why they were replaced. A newer style one will fit perfectly.

The early one is a push in type to open it.

The later one if you get the complete unit screws straight in, straight swap.

The later one can also go wrong but if it does there is a solution by drilling a hole in it so it remains totally usable. Its on the forum here. The wise would have the hole drilled and bunged!!!

Thanks for the replies everyone. That's very interesting. What is the mode of failure on these old ones?

I haven't handled one in a while but the high level issue is that the early ones have a "button" that can be left locked or unlocked.  The latter caps are much simpler in that you just turn a key each time to open it so the internal mechanicals are much simpler and less prone to failure.

Ah I see. I think I'm going to cut a gasket myself as a short term solution. Later on I'll up fit the non-push button versions. Thanks again for the help!