Tank Blisters

You will need to empty the tank, let it dry out and then seal the inside with an ethanol proofing product. In all honesty, if it's badly blistered you'd be better off finding a decent replacement and sealing that before you fit it.

I think it was Flowliner that I used on mine.

 

As @Gladtobebackontwowheels says, you might be better to find a replacement tank.
I’ve heard of people who’ve sealed and repainted plastic tanks that have blistered and they’ve later blistered again.
I bought another tank for my Daytona and have been leaving it for a while to thoroughly dry out before sealing and repainting (mainly cos I’ve not got round to it yet )

 

Ethanol free petrol is the way to go. But ...... that means using super unleaded which can be very expensive and even that is not guaranteed to always be ethanol free, particularly as future supplies will have to contain the evil shite!

 

It' caused by Ethanol in the fuel which draws water - it's a combination of the water/ethanol that causes the issue
The blisters are not actually in the Acerbis plactic itself - it is coated with a thin 'filler' type material and this is what gets the bubble, between the plastic and that outer 'skin' - you can actually sand through this and re-level it, but of course would require a re-paint.

 

Also consider doing Epoxy Liner - company called Caswell Plating makes a 2-part Epoxy kit specifically for this application - I did that on mine prior to painting
Another failure prone issue of these tanks is the tubes that go from the filler neck down to the drains on the left side - it's not uncommon for these to develop holes with a resultant leak of fuel into the tubes and a constant drip from them. Mine would leak when tank was over half-full and then stop below that level. The Epoxy will also coat those tubes in the process to prevent that.
Certainly if your tank is not too bad yet and not bad enough for a re-paint then absolutely do the Caswell Liner

 

I just bought a baglux cover for my last one.
My current Tiger 955i has no blisters at all.....last of the production run.
If it develops them( 30k so far and no blisters) I'll buy another baglux.

 

The baglux is not preventing anything - problem is coming from the inside, not the outside.
Do you perhaps use non-Ethanol gas? (or were at least for it's majority life)
Unless you just mean to hide them with the cover ........

 

I just mean to hide them with the cover.
Exactly that.

 

I bloody hate tank covers!

 

I hate the blisters even more.