Even though the oil tank cap rubber washers have worked well, it was found that the fuel tank washers swelled up after a while despite being claimed to be fuel proof. Once allowed to dry out they were good to use again. If anyone ordered one, they would be supplied two.

After a long fight, I now have Leather versions. They are quite thick, but my experiments have shown anything thinner doesn't last very long.

https://pesltd.uk/?product=66-8360L

https://pesltd.uk/?product=66-8361L

Mark

email (option): pes.sales@btconnect.com

Leather is a good choice. Some older Italian bikes used leather from the factory for the fuel cap. It swells up when the fuel touches it and seals even better.

The fuel and oil cap seals that I was selling for Robb Nortier were made of leather, and I can vouch that they worked well and lasted for years. Ron

email (option): ronpier@talk21.com

The original seals that I've seen on Enots caps seem to have been a sort of laminated gasket paper material. They're quite thin and the use of thicker gaskets stops the caps sitting squarely, so they leak. Cork or leather work on the bayonet fitting types, but are compromised on the hinged caps if they are too thick to allow the cap to close fully.

Wow Rik, I'm lucky I know what I'm doing then.

Mark

email (option): pes.sales@btconnect.com

I've tried a number of different materials on the hinged type of caps and have concluded leather definitely gives the best combination of effective sealing and longevity...
When the 'mechanism' of the cap is fully loosened there is clearance between the underside of the cap and the top edge of the filler neck that it sits on...It is plain that if the gasket material is too thick the cap will not sit squarely on the neck as the cap pivots through an arc...In that case the 'arms' of the mechanism would not pick up correctly in the groove in the filler neck which the arms pull against/into when the cap is tightened...The clearance is really governed by the amount of slack between the split pin that retains the cap and the hole it fit into as that determines the amount of free vertical movement of the cap...I'd assume that Mark has determined that his gaskets are not too thick and function correctly and that he has calculated the maximum clearance and then made the washers an appropriate thickness.....Ian

Fortunately, it seems, that the cattle in Yorkshire are as thin-skinned as the engineers so everything is fine.

Thanks, Ian, for your explanation.
I did my 30 miles test circuit last night (bsa club) and not a drop of fuel or oil leaked, well not from the caps.
Also, the new PES steel clutch plates performed better than expected.
These will be added to the website shortly.

Mark

email (option): pes.sales@btconnect.com