Reddit reviews Caswell Epoxy Car Gas Tank Sealer - Up to 20 Gal, 1 Quart

tipo isso? https://www.amazon.com/Caswell-Epoxy-Gas-Tank-Sealer/dp/B009T8BUG2

agreeing with everything /u/Alfa_Alesi said, but just my suggestion to help the situation you're currently in;

1. remove the tank from the bike, drain and dry the inside of the it thoroughly (im talking hot air blowing through it for about 24 hours type of dry)
   
   
2. clean the inside with a dry lint free or micro-fiber cloth and remove all internal components
   
   
3. order you up some caswell tank sealant and follow the directions on that bad boy
   
   
4. do your best to search for non-ethanol gas stations in your area and stick with those.
   
   it really depends on where you are, some places in the USA have next to none in a 500 mile radius, and some places have 'em on every corner. where i live here they're really sparse, so i keep a few of the 5 gallon cans in my garage and just top off my bike every time i go for a ride.
   
   Here's a site that helps. but if you can't find non-ethanol close by, the fuel treatment stuff is your next best choice. i haven't used any myself yet, so i can't entirely recommend a particular product for ya. i just stick with non-ethanol stations exclusively.
   
   oh and for long term storage, (say maybe over the winter) keeping the tank completely full will help prevent that spotting, and fuel stabilizer helps the gas from going rotten.
   
   hope this all helps