DDK - Die Deutschen Klassiker

I've tried copper, aluminium, teflon and fibre washers to try to seal the tank where the fuel outlet pipe screws on.

I have sealed the 10mm side with a copper crush washer and there is no problem there but the 8mm side will not seal.

The best result i had was with the aluminium flat washer but for some reason it started seeping. Last night i resecured the joint with a teflon washer but this morning i've woken up to the smell of petrol again!

Any ideas?

I think you will find that one of the mating surfaces is slightly damaged/dented so whatever washer you use will not work correctly. Hopefully it is the fitting that has the issue and not the tank.

Cheers