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Message started by engineer on 09/21/12 at 08:02:48

Title: Gas tank rust
Post by engineer on 09/21/12 at 08:02:48

Hello: This isn't specific to the Savage but it does apply to any motorcycle with a steel gas tank. I am restoring an old Honda CB125s and the carb kept collecting what looked like extremely fine rust particles mixed with some gooey old gas. The inside of the tank looked pretty good so I cleaned it out with hot water and Dawn and not much came out of it. I then bought a gallon of Evapo-rust at Autozone for $22, poured it in and let the tank soak in different positions over a couple days. Anyway the inside looks good now.

My question is should I use a sealer like Redcoat or just leave it be and keep it full of gas? The petcock hole is very small, like a small pipe nipple, and there are internal crossover tubes and I have been told that sealers can permanently block those up. Is there a sealer that isn't so thick? The tank doesn't leak, it just needs something to keep the rust from reforming.

The Evapo-rust is nice to work with, it doesn't bother paint, rubber, or your hands but it is not as fast as acid.

Title: Re: Gas tank rust
Post by srinath on 09/21/12 at 08:06:16

The gas of today has so much alcohol in it that it makes no difference whether you keep it full or not it will rust.
I'd coat it, however redkote I have not used ... I've used POR15 and kreem, like em both for different reasons and hate em for different reasons too.
Cool.
Srinath.

Title: Re: Gas tank rust
Post by Spamy on 09/21/12 at 11:45:05

Good question.

Ive had mixed results with Kreem the 2 times I used it. One time it started coming loose and was a nightmare. Since then I have decided to leave my tanks bare and just clean them when needed.

I would be curious to hear real results from people that have had lasting success. Not, "I did it a week ago and its awesome". I want someone with actual valuable feedback.

Title: Re: Gas tank rust
Post by justin_o_guy2 on 09/21/12 at 22:11:59

Keep an eye on it, when it has a fairly complete haze of rust, drain it, remove it, dump a cup of Jasco ( formerly Ospho) in it & shake it around. Do that a few times,, once its All been rusted & all been treated Without Any of it being allowed to rust to the point of making a flake, all just surface rust, YOu get the whole tank treated & turned black & made into Iron Phosphate, I dont think itll rust again,
The inside of the wheel on the backhoe is black from the Ospho I put on it a coupla years ago.When I had a flat I looked at it, I expected to need to treat rust. It was wet in there, a little, certainly not dry & I used a torch & heated it enough to hammer it into shape. I dont mean just a few little dings, it was wrecked,, took about 3 days of working & thinking,So, Dilute Phosphoric Acid treats rust, tranmsforms rust to Iron Phosphate, & prevents rust.

Title: Re: Gas tank rust
Post by engineer on 09/22/12 at 04:50:08

Thanks for the tips. There seem to be a lot of reports of sealer jobs gone bad and since some of the original coating, galvinizing or whatever, is still left in this tank I think I will do the phospate treatment. I will also install a good inline fuel filter.

Title: Re: Gas tank rust
Post by Greg-E on 09/22/12 at 18:44:09

The filter is probably the cheapest way to prevent carb clogging.

Title: Re: Gas tank rust
Post by justin_o_guy2 on 09/22/12 at 21:37:49

& it lets you see whats comin thru the petcock. If youre seeing much stuff in the filter, you know the screen on the petcock is getting a load,.

Title: Re: Gas tank rust
Post by Mr.Orange on 09/23/12 at 14:45:35

Mines pretty rusted. Just recently took everything apart and found tons of rust around the petcock filter and inside the carb where the fuel line goes in from tank. Was giving me hell with "get up and go" now its back to acting up. In process of taking apart again. Would love to get that rust out.

Title: Re: Gas tank rust
Post by justin_o_guy2 on 09/23/12 at 16:50:49

If its built up into layers, youve gotta get it out, down to the first sign of rust. The phosphoric acid cant react with what it cant get wet, so, all that would be accomplished is to change the upper parts, the rust down below would continue to grow.

IDK what products are avilable to soak rust flakes out, surely theres something out there,,All Ive ever done to deal with rust has been external.