Wow that's weird. I put SEA FOAM in my tank on all my bikes & cars. I know for sure there is no rust in the o4 Bonnie and No rust in my baby the 76 Bonnie. Think I would pull the tank and have it cleaned. Bunch of different ways to do that. Get er done.

 

What is Sea Foam?

 

If you really believe it is a serious problem, you could try using a POR-15 kit. A lot of people swear by it, but it's a fairly involved process.

 

there's a goo called Kreme in 3 cans

1st can is an etching acid
2nd can is a neutralizing flush
3rd can is a white rubbery sealing goo

the theory is clean what you can and glue the rest in place...it's used on old bike restorations and I think it came in HD and BMW steel tanks.

I've had the stuff on my shelf for a couple years unopened.

I'd just put some bolts or stones in the tank shake the snot out of it and knock the loose stuff off, then put an easily replaceable inline filter...and use dry gas to keep the condensation out of the tank.

your bike sits outside?...that's common.
keep the tank full in the cold.

 

Sea Foam

Have neighbor who uses it in his ATVs and bikes. swears by it. I haven't used it myself.From their web site:

100% Pure Petroleum
Use in All Engines in All Seasons
2 Cycle, 4 Cycle, and Diesels
Treats 3 Critical Areas: Gas Tank, Fuel Systems, and Crankcase

Cleans fuel injectors, cleans carburetor jets, Cleans carbon, Stabilizes fuels,
Upper cylinder lube, Removes moisture in fuel, De-icer, Frees sticky lifters
Frees sticky rings, Removes moisture in oil, Cleans P.C.V. systems, Cleans catalytic converter odors, Oxygen sensor safe.

http://www.seafoamsales.com/motorTuneUpTechGas.htm

Ride and Enjoy!

 

Sea Foam is a additive that you put in you fuel. Think it was invented in the British Isle to combat there type of climate. Use it in inboard, out board motors. Motorcycle etc. Really good stuff. I get mind at NAPA> Also good for cleaning out the carbs or jets on anything.Try it you will like it.

 

"it's (Kreme) used on old bike restorations and I think it came in HD and BMW steel tanks."

Modre, the insides of both BMW and HD tanks were (are) painted; I don't believe any other other type of coating is used, but today, who knows.

Kreme has both proponents and detractors; I think the issues are proper preparation and compatibility with some fuels. I've heard fewer negative reports about POR15, but I'm sure preparation is still just as important.

But we're discussing solutions for bikes that are more like decades old, not the latest generation Bonnies. If you have a minor rust problem get rid of the rust and you should be fine. Coating is a major PIA, involves very nasty chemicals, and if not done properly can essentially ruin your tank (or at least your wallet).

As for removing rust, I imagine some of the chemicals used to etch the tank and which come with Kreme and perhaps POR15 should work fine. I believe these are mild acids like mercuric acid; some research or advice from someone who has the definative answer is required. Others use mechanical means of cleaning up the insides of their tanks; like dropping in a couple of hand full’s of small nuts and bolts and shaking vigorously.

In any case, start simple, get the rust out, and keep it out by removing condensation with something like Seafoam one in a while.