Hello! the thread of my M20 fuel tank have 5/8 and it have reductions to 3/8 BSP.
I need to know the original thread of the deposit, if they had reductor thread and the petrol tap threads.
Thanks.

Hi Alex...The thread used in the BSA petrol tank and on the taps is BSPF (British Pipe Fastener Thread), the 'F' indicating that it is a parallel thread.
The listed size of a pipe thread is not indicative of its outside diameter...for example 3/8" BSPF has an outside diameter of .656, 1/4" an outside diameter of .518". The thread into the petrol tank is 3/8" BSPF and the internal thread of the adapter and the thread on the tap are 1/4" BSPF.
There are two variants of tap and petrol pipe nuts. Some taps (and pipe nuts) have 1/4" BSPF threads and some 1/8" BSPF. All taps are 1/4" at the tank end...Ian

email (option): julie@wright52.plus.com

Thanks Ian, I did't know, four month ago I bought two taps and as I had not repair the tank I did not fit it but now I see that they haven't the same thread of the tank, I am Spanish!!

i dont know whether your gas pipe fittings are the same threads in spain but i got some of my fitting from my local plumbers suppliers i am not sure what you are looking for exactly but if we can work it out i will try and get you some here

email (option): roger.back@node6.com

My problem was that most of the thread are BSW and BSF, so I thought that it could be 5/8 BSF instead of 3/8 GAS. But now there are not problem, thanks!