Tank paint issues

[Dads bike]

Gents
Has there been a change to fuel in the UK in the last 12 months?
I was reading a comment by tck regarding blistering paint around the filler neck on a newly finished tank. I have found myself in a similar position, only my tank was re chromed and re enamelled in 1970.
Over the last 50 years I have left any remaining fuel in my tank over the winter period, draining it out and filling with fresh about this time of year with no impact to the tank finish. Note the tank is not lined internally.
A couple of days ago I started the annual refresh, only to find the fuel cap well an truly stuck. Eventually upon its release I found the paint internal of the tank cap seal well compromised, why the sudden change?

Steve

[Hamwic]

I suspect that is the effect of ethanol in the petrol. I have suffered similar issues over the last couple of years, the worst effect being to the allegedly "Ethanol Proof" taps fitted to an alloy tank on an Inter Norton. The taps seized solid as the nylon seal had expanded, and the brass filters within the nylon supports had all but dissolved away. This was said to be because of the galvanic effects of the dissimilar metals, but the vapour also lifts almost any paint.

You really have to drain the fuel right out, ands also run the carbs dry. If there was fuel in your carbs, you should also check the brass needles and needle jets for corrosion damage.

Doug