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Kymco People GTi 300 Review

Fuel Tank Cleaning

Restore Flat Black Plastic 

Cleaning a Rusty Motorcycle Fuel Tank

Funny thing - I was recently looking over a friend's newest motorcycle acquisition (an older Honda 4-cylinder) and wondering how we were going to clean out the rusty tank without damaging the exterior paint which was still in great shape. Thanks to Greg Stewart (aka ScooterBob), now I know - Editor

I often have to clean tragic rust from a motorcycles’ fuel tank in order to facilitate using it again. It is NOT often, however, that I run into a perfect original paint tank with more rust than the Titanic on the inside. Usually, I can be as brutal as need be (sand blasting!) to remove the rust as well as the finish on the outside for re-coating. This was not the case for the Triumph Trophy that I was in the throes of getting back on the road again. The bike was very gently used – but stored, apparently for some time, with that miserable, corrosive excuse for pump fuel that we now are forced to endure with our antique and vintage motorcycles. The inside of the tank was a WRECK – and I was quite hesitant to clean it using “traditional methods”.

You often hear about “putting rocks” or nuts and bolts or BB’s in the tank and swishing them around to clean it. This only works for the most mildly affected tanks – and all have their drawbacks. Rocks can be TOO big and cause pimpling from the inside out on the tank. Nuts and bolts, as well as BB’s are too often hard to get back OUT of the tank once they have been swished. I usually use a length of porch swing chain – which is pretty abrasive, not too heavy and WILL come back out in one piece – but I thought I’d use some “tricks” on this particular tank since the rust was SO bad and the paint was so good.

Research told me that electrolysis was THE way to remove the barnacles from the inside of the tank. Add a brine (electrolyte) solution, install a cathode, add a little current and the rust will magically melt away before you very eyes. I used iron nails for the cathodes – and once I found a method to suspend them in the tank – I turned on the current and waited. The problem was that the nails would attract the rust, alright – but I think the inside of the tank was rusting in the brine faster than the electrolysis could remove it!! A couple of weeks of experiments on that and I officially declared the method bullshit and went about the search for a good cleaning method that would actually REMOVE the pounds of red, scaly rust in the tank. What I came up with involved a good deal of work – but the results were outstanding!

Fabricating a tool to clean rust from a mtorcycle fuel tank

I started by fabricating a copper “scraper” from a piece of copper rod to remove the scale without gouging the steel of the tank. Copper was also chosen as it wouldn’t make sparks within the tank and ruin the paint by turning it inside out with an explosion of residual fuel! After a few hours of painstakingly scraping the interior, bit by bit, feeling for rust in the areas that even the borescope couldn’t get to, I was ready to surface prep the interior. I made yet another tool to do this operation with – and the results were better than I’d have hoped for. It was an Cleaning rust from fuel tank with homemade toolafternoon well spent. The rod got “gently” flattened on one end to be used for scaling the inside of the tank.The next step was to form the end into t a scraper blade that would be sharp enough to remove the scale – but have no corners to dent the tank from the inside when force was applied.

The scraper could also be bent in a variety of different ways to facilitate scraping ALL of the inside of the tank – from the ever hard to reach “far side” to the underside of the top. The rod was bent, re-bent and sharpened about a dozen times during the rust removal process.

The next “trick” was to make a sander that would address the interior surfaces toHomemade dragonfly tool carefully finish the metal that had just been scraped. I used copper wire, again, to keep from sparking and gouging the interior surfaces of the tank. A strip of emery cloth was captured in the twists of the wire and more strips were added to make a crude “brush”. This worked so well that I had to leave to shop to allow the rust dust to dissipate! Here is the “dragonfly”

Now the tank is rinsed with a light petroleum solvent and dried and ready to line! The result will be that the remaining rust will be encapsulated, the interior of the tank will be coated and rotten fuel will never again corrode the precious metal on the inside of this tank again!

Rust cleaned from inside a motorcycle tank

Greg Stewart
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