Leaking petrol filler cap

Thanks for the responses. Yes, first thing I did was check that the mating edge of the filler opening is flat, but I can check again. And, it's not the original tank â sadly that was trashed in a traffic accident, when the bike was parked, believe it or not â? Fortunately the person responsible was traced and repairs paid for by their insurers. But the tank was NOS; and it takes firm pressure to close the filler, so I've been assuming that the seal is held squarely against the filler opening by the spring that's behind it. But I can check that too. If I find anything I've missed I'll report back.In the meantime, I'd still be very grateful for pointers as to the material and dimensions of the hose-like part in AN's filler cap service kit. Cheers.

The breather holes in mine are 90? apart (and clear), and too small to explain the amount that comes out â it doesn't slop out exactly, but for example braking to stop at traffic lights with a full tank produces a thin stream over the paint.

It just occurred to me to try holding the seal over the filler mouth, so one finger blocked the central hole for the screw and applied pressure, and another blocked the breather hole â then opening one fuel tap and blowing in. The tank's off the bike and empty, you see. A jet of air came from just where the fuel does, about 10?â15? east of north, if I take the front of the tank to be north. Obviously I'll have to take a closer look â? Thanks again for contributions so far!

Ok, well, there's a thing â? I smeared washing up liquid around the filler mouth and pressed the seal against it â the seal picked up the washing up liquid in a perfect ring, no gaps. Then I tried the same with a small plate of safety glass, with the same result â this time a complete ring of washing up liquid was clearly visible through the glass, squished between it and the filler opening. Which pretty much takes me back to square one, I think?

The only thing I've noticed is that the rubber disc that forms the seal isn't quite central in the steel pressing. Perhaps that's it.

I started off asking after the hose-like part of AN's kit because I assumed that it must be my attempt to replicate it that was inadequate â from the way the seal is attached to the cap, I assume that part acts as a secondary seal around the screw, behind the seal disc. Maybe I should just shell out for the AN kit and see what happens with a new seal-and-pressed-steel-disc part from CEANDESS of Wolverhampton! Poor old piggy bank â?

Thanks again for the responses! It might take a while for me to get hold of that kit and try it out, but when I do, and if I remember, I'll report back. Cheers.