The permanent cure for plastic tanks...
It's considerably lighter in weight and it holds more fuel (which I suppose negates the lighter weight) but at least it doesn't expand. Problem solved. View attachment 993245
I recently bought a spare stock tank. I might consider an alloy tank as a permanent cure, but at the price they charge it would have to be a thing of beauty, because the prices I’ve seen for an S4RS replacement tank are beyond what I would consider reasonable for the product I’m seeing. The one StraDuc posted is more what I’m looking for, and it’s probably more than I’d be willing to pay.
Mine was one of the early ones bought from Motowheels that was made in Italy by the same company that (allegedly) makes the tanks for Ferrari. The owner of the company has a PS1000. He also made seat cowls in alloy for Mono's which although I really wanted one I couldn't justify the price for a cosmetic rather than a safety related part. The later batches of tanks obtained by Motowheels were a bit better than the first batch I think. It was a Christmas gift (2012) from my wife who is obviously a keeper. They were around $2K but considering what a new unswollen plastic tank and a professional interior coating (that could be less than permanent) would have cost I thought a for sure permanent fix was worth the additional cost since I had no plans to ever sell the bike. It was a PIA to fit to the bike and it shows some made by hand idiosyncrasies in the fit and finish that don't bother me and it has been trouble free for 8 years. The maker still occasionally posts tanks and cowls on Italy eBay. My tank is a serviceable piece but If you want a perfect work of art alloy tank get one from Evan Wilcox. I don't think anyone on the planet is a better aluminum beater than him.
This is a pic from about 4 years ago in the Driftless region of SW Wisconsin. The tank is still nice and shiny. I rode it today and it still looks the same and I haven't polished it in several years. The black Biposto was recently bought from my riding buddy Tom by lister Mike Delphin.