Just been scanning the bay of e for a filler cap and surround the costs are quite high. Is there any reason why a bike cap and surroung cant be used. They are way cheaper and in abundance

yep. you'll struggle to find one with a funnel for a fuel filler pipe to attach to on a bike filler. bike fuel caps go right on the tank so they don't have a filler pipe (as you'll know) and a car will need a funnel attachment
you can buy them, but by the time you add the cost of that, you're about the same price as a non bike one

[Edited on 1/1/10 by blakep82]

bar the above its a great idea

I went to a scrappy and got a cap and filler neck from a Bedford Rascal. The cap is situated under my rear tonneau, is easy to get to, out of sight and fills as fast as the pump goes