Acerbis Tank please help!
 

Hey, Im not sure where to post this but hopefully this is the correct place??? I recently bought a second hand long range acerbis tank for the bike. When I recived it I noticed that the previous owner of the tank had covered the two petrol taps inside and out in some kind of silicon meaning I couldnt use the reserve (whats the point in having the tank if you cant use the reserve?!?!?!?). So I bought some new taps, and it was once I removed the old taps that I realised why he had done this....rather then having a round hole for the tap to slip into as normal, alowing the small washer to do its job and stop the petrol leaking, someone has bored a bit away from each hole making them oval! So the small washer no longer works and the tank leaks. I have cut an old innertube to fit between the petrol tap and the tank which has stoped the leak, and its been fine for the past 2 or 3 weeks, but I think that the petrol will eventually rot through the innertube patch and start leaking, and the last thing I want is to be in the middle of nowhere when this happens. I havnt been able to find any washers wide enough to cover the extra bit of hole. So my question is...is there any kind of silicon or something that I can patch this hole with?I can use fiber glass or anything like that as remember its an enlargment of the hole that the tube on the petrol tap gos through. How long do you think it will be untill the inner tube starts to rot? In in the uk so if you know of any products or shops here a link would be great. Thanks alot, hope someone can help. Cheers!!!

You don't say what material its made of but if its glassfiber, it can be reapired. The rule is to grind 10 times wider than the thickness of the repair: a 1 mm plate should be ground down in a 10mm circle and then fill it out with fiberglass.
You could also glass in a piece of metal sheet with the correct hole in it.

Or just have a bigger washer made.