Old Gas in Tank

Most of the threads I searched related to cleaning a gas tank have to do with rust. Fortunately, I don't have a problem with rust. The issue is that the bike has been sitting for a couple of years with gas in the tank. I cleaned the carbs and they were gummed up bad. I figure the inside of the tank is probably gummed up some too. Of course I am going to empty the tank and put fresh fuel in. But before I do so, I want to clean out the tank so there is no residual varnish left in the tank.

Suggestions please.

Thanks.

Take the petcock assembly off and clean it separately. If the gas oxidized in the tank, it will be like sticky varnish. Fresh gas will help but may not get it all. A strong solvent like acetone is better but be careful not to let it hit any painted surfaces. You could also use a typical carb spray cleaner into the tank, same warning about paint damage.

A safer approach would be using a gallon or 2 of white vinegar & shaking it around for a couple of days, wont harm paint like acetone will
Pete