The CB1100 Community Forum

I've just had a strange whistling noise coming from the fuel tank. I was concerned it was the fuel pump, but running the bike with the fuel cap open made the noise go away. My friendly neighbourhood mechanic reckoned it was likely a blockage in a tiny air vent in the filler cap and suggested I had a go at cleaning it up as the alternative would be to buy a new one. Of course, if one had an old bike like a 1969 Honda CB750, one could pull the thing apart, clean it up and even install a new gasket. Not any more. Honda would like you to replace the whole thing at a cost north of AU$100. I'm not confident that, if I got it apart, it would go back together.

Anyway, putting aside the grizzle, I took the cap off and cleaned it up as best I could, including giving it a bath in vinegar. I think I found the two little breather holes and scratched some crud out of them with a needle. I've run the bike for 10 minutes or so and the noise hasn't started again, so here's hoping.

However, I also noted that the spring which compresses to allow the lock tangs to spring out is working ok on one side but not the other. It makes it a bit hard to close the cap easily as the key does not simply spring back. Ideally one would pull it apart and clean the spring up, but I can't see how to do that and I'm not keen on breaking it.

Does anyone have any suggestions? Please?

I don't know how prevalent gun cleaning supplies are in your neck of the woods, but hitting the lock with some nitro solvent, blowing it out with some compressed air, and lubing it with dry lube might help with that.
Make sure the lock is fully dried out before applying the dry lube. You don't want to cake it up inside.

Huh. Mine doesn't always spring back either. Sometimes I need to turn the key and help it a bit. Guess I'd better clean and lube it. Thanks for the tip, Randy!

Thanks for the tip, Randy.

Maybe instead of a needle, scrape off a plastic wire twistie to get to bare wire and use it to insert into the breather holes.

Good thought, pdedse.

(05-16-2026, 09:07 AM)pdedse Wrote: [ -> ]Maybe instead of a needle, scrape off a plastic wire twistie to get to bare wire and use it to insert into the breather holes.

A piece of wire from a wire brush is also a good alternative, if it is long enough. Inexpensive and usually around the shed someplace.

I used to use single strand wire to clean carburetor passages.

Check this, might be helpful for disassembling the fuel cap.

https://youtu.be/zPpTess4_pE?is=jGurchbsy79Xo9u1

Thanks McGyver. I'll need a new roll of tape before embarking on that!

Seriously, it looks really helpful.