I have a 2002 Sherco 50 and the fuel tank is leaking. I tried patching it with epoxy, fiberglass, fuel tank repair, and even plastic weld it and the best I could get was about 3 months use then it starts leaking again,  I tried to buy a new gas tank here in the United States but no one has one,  So I'm giving a shout to you folks in Europe to see if you can help, PLEASE Does anyone know where I can buy a fuel tank for a 2002 sherco50? 

Caswell's tank liner??

Not affected by modern fuels.

It may help if you let the forum know exactly where on the tank it is leaking.

I had the same problem I think, on mine the adhesive that holds the petrol tap boss in deteriorated and subsequently caused it to leak. As you have done, I tried everything but because the tank is flexible it soon cracked and started leaking again.

I did source a new one through Malcolm Rathmell Sport but that was about 2 years ago so I don't know if they are still available.

In the end I was told about a substance called SIKAFLEX, Its like a black mastic but much better. Its flexible, sticks like s--- to a blanket and seems to be petrol or Benzine resistant. I sealed the tank probably 2 years ago and its still petrol tight.

Hope this is of some help 

I finally built a tank out of aluminum.  Works fairly well I did loose some capacity and I had to insulate it from the heat of the engine but, I'm not fighting the leaking petcock mount.