Rubber woes with Indian C15 tank

[Tigerfeet]

Has anyone got any bright ideas for reducing the diameter of stock rubber components?  I thought I had dealt with all of the issues relating to fitting a 'Made in India' replica petrol tank - but I had missed the fact that the central mounting hole is a smaller diameter than the BSA dimension. This means that the standard 'expanding rubber doorstop' is too fat, as is the BSA bung that fits in the top. So I need some way of shaving a millimetre or two off the diameter of both. An hour or so with a scalpel would no doubt do it. But is there a better way?

[neil1964]

I had same issue with the alloy tank on my B34.
I whittled with a nice new sharp scalpel (Number 23!)

[rhyatt]

Would a pad sander work ?

[Novocastrian]

A Dremel would quickly reduce that... It works on the skin on my feet very well

[Stubaker58]

I have the issue with what looks like an original C15 alloy tank.

I was thinking of putting the whole central fixing into a drill then holding sandpaper to the rubber and switching on!

[martinh10]

Bench grinder. Rubber can be ground quite accurately with a fine grinding wheel - just don't let it grab.