Rust or Varnish

I just got a bike which hasn't run in 14 years. The PO left it sitting with gas in the tank.

When I looked inside the tank, it looked like it was covered in rust.

However, when I drained the old fuel, it came out almost golden in color. And it smelled vaguely of ammonia.

So.... do I have rust in the tank or just a heckuva lot of varnish?

How would I check? I thought about spraying in some carb cleaner but, I had run out. So, before I head to the parts shop and pick up some, I thought I would ask to see if there was something better.

And if rust, should I use redkote, kreem or por-15 or just clean it and run some ATF fluid inside of the tank and swish it around and hope for the best?

Thanks, Dan

 

I forget to add, when I drained the gas out, the funnel I used to direct the old gas had a strainer in it and there didn't seem to be any sediment in it.

The strainer could have been too open to catch it but.....

 

Sounds like probably varnish. If the tank was full that is a good sign.

After it dries rust will have a matte finish, where varnish tends to be a bit glossy.

 

I'd say you probably have both - rust in the upper areas where it was just air & fuel vapour, and varnish in the bottom corners of the tanks where you can't see. DEFINITELY give a close look at the petcock and make sure it isn't all gummed up too.

If you haven't got any holes or potential holes in the tank, I'd reccomend cleaning the inside chemically (fuel cleaner, alcohol, paint thinner - whatever).

After that's clean and dry I'd suggest the electrolysis method of relining the tank with new metal to replace the rusted stuff -- there's instructions around for using a high-power battery charger, galvanized steel rod, and salt water to make your tank look like new.

Otherwise, you can clean the inside mechanically (handful of screws/bolts/abrasive media and shake the bejezus out of it), and/or clean chemically as above.

Unless you've got some spots threatening to leak, an interior coating really isn't needed. But if you really want to add it, stay away from the Kreem stuff and go for the professional level stuff like POR15.

 

My car trailer was completely caked with rust... real bad.. i poured on some muratic acid (home depot $10) and it took all the rust off... make sure you don't breathe it and wear proper PPE ...

 

Lets say I am going to clean a tank out with Muratic acid, how long at what mixture? Then how do you get the water all out after rinsing? After it is dry would fogging oil be a good idea?