Right,Cookster! The acid treatment is a lot easier when you have a removable tank.If it were mine.,I wouldn't sand-blast it,I'd do the acid thing.But see,I'm a Chemical Operator and have been flushing and cleaning for years.That's why I recommend a water hose be handy that's within reach with your eyes closed.We use pressurized portable eyewashes out in the field work.Here's what I'd do if it were my bike:Drain the gas,fill the tank with used or new motor oil, drain this out,drain yourengine gearbox, remove any battery or other liquids,and HANG the bike upside-down so the gas cap opening is bottommost.Take a 3/8" cable about14" long or so and fray one end ,also bending it 45-90'. Chuck the other end into a 1/2" drill and that cable will knock the worst rust out of the tank without hurting or denting it.Then take an air hose(you've got goggles on now)and blow the heck out of the inside of that tank.Check the inside for particles that don't blow out and get them out also;then blow it out again.Restore the bike upright,remove the old no-good petcock,and flush thru the tank with a generous amount of gas, and install your new petcock and filter.Fill her with all the fluids you removed and start her up.Check your fuel flow by removing the hose at the carb every so often and you'll know if you need to remove the petcock valve and clean the filter.Use gas without ethanol and methanol and you'll keep rusty tanks to a minimum.(MARATHON or SHELL is good) BYE!