Britbike forum Forums British motorcycles in general British motorcycles in general gas tank cleaning

I've taken on the task of getting a neighbors Kawasaki KLR running after a 4or 5 year sleep. I know, its not Brit but it's still s nice bike. The carb and tank are gummed up with very old gas and Marvel Mystery oil. He always ran non ethanol fuel so there is no rust, but whats in the tank is like tar and smelled like the old gas smell I remembered back in the good old days of leaded premium pump gas. I'm thinking that a good soak and rinse with dry gas (alcohol) will melt/loosen/dissolve the mung in the tank maybe? The carb is coming clean with a soak in Hydro Seal but thats not practical for the tank.

You need more gasoline. Fire with fire kinda work

You might try "white gas," which is what is used in Coleman lamps and camp stoves.

Available in gallon cans at sporting goods stores and some hardware stores.

Very flammable, but pure, and can act as a solvent to dissolve old car fuel gasoline.

Coleman fuel is Naphtha

Acetone and drywall screws. Shaken, not stirred.

When it looks perfectly clean, add fuel and start motor. You may find vibration has loosened even more hardened fuel and has clogged the taps. Rinse and repeat...

I have used lacquer thinner to dissolve coating/crap in gas tanks, sometimes with lots of old screws, shaken not stirred. When I am satisfied that the coatings, etc are gone, I treat the tank with phosporic acid, sold at Home Depot or Lowes as "Klean Strip, Phosphoric Prep and Etch", which works over the rust. Length of time depends on the amount of corrosion. When its done, l rinse with lacquer thinner, let dry, and it is ready for gas. Pretty simple, cheap, and not too difficult. Obviously, if the tank has paint you wish to save, you probably should another solvent or just hot, soapy water and air dry

I have user varioius pour in tank carb cleaners in the past. See what walmart has on sale.

Right! I use a phosphoric acid treatment that leaves a coating of zinc to prevent flash rusting. It’s a PPG product that is available from auto paint distributers. If the tank will not be used right away, I would coat the inside with clean motor oil. This can be easily rinsed out later with gas.

And the name of that product would be?????

Sorry, when I wrote my comment I didn’t feel like going out to the garage .

PPG DX520 but that was years ago. Might now be SX520. I haven’t purchased any in a while. I also use it to remove rust from small hardware bits, nuts, bolts, etc. I soak them in a glass jar. You have to monitor the process. The stuff is pretty aggressive. It makes bubbles when working. When done I screw the cap on and save it until next time. Beware of sticker shock - $35 for a quart!

SEM makes a similar product called Rust Mort. I've also used Evap-O-Rust for the same thing.
As a followup, I gave the tank back to the bikes owner and told him to have a go at it. He used acetone to get the sludge out then did the hand full of screws and shake trick. Worked fine.

Pardon me if I'm stating the obvious, but remove the petcock(s) before cleaning the tank. I know, it's a PITA because then you have to plug the hole(s), but you don't want to destroy screen filters which may be on the petcocks.