How to paint a plastic fuel tank and use it normally

Spoiler alert: it is easy, but... don't

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The starting point

The old Vesco tank I had bought off eBay for the Baja Commander replica was in very good condition, but the color was not right.

I contemplated buying a brand new equivalent from Clarke (apparently, Clarke had bought Vesco's shapes back in the day), but even with paying over $200 I wasn't sure I would get the right color.

First, learn

So I searched the internet for the right way to paint a plastic fuel tank. The results of my searches were not totally satisfactory. I did find procedures to paint plastic but none of them guaranteed that I could use the tank normally.

There were two challenges to overcome:

  • making the paint stick to the plastic

  • keeping the fuel fumes inside the tank

I had no idea what plastic the Vesco tank was made off but this did not seem to matter to my fore-bearers. So here is what I did.

Mechanic Working on Motorcycle
Motorcycle Club

Special materials

  • acetone

  • fuel tank liner from Blueligthning Products

  • adhesion promoter spray can from SEM

  • flexible primer from SEM

  • (zinc plating kit)

Procedure

  1. Thoroughly washed the tank inside and outside with acetone several times over several days, weekends to remove any trace of old fuel, grease etc

  2. Removed rust and zinc plated the metal piece of the tank opening. Obviously this has a lot of sub-steps but not the point of this article.

  3. Poured a pound of wood screws inside the tank, wrapped it in a blanket, and ran it for 30 min in a wash-drier. The intent was to roughen up the inside for the liner to grip well.

  4. One more shot of acetone inside and left everything to dry thoroughly

  5. Lined the inside of the tank as per method indicated on the can. This is a little strange as the liner takes a long time to dry. When left overnight, most of it sets at the lowest point and I wasn't sure there was any liner left on the other parts of the tank. So I did it twice over two week ends. The liner is a super thin and hard green layer.

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Procedure 2

  1. Sanded the exterior of the tank

  2. Cleaned again with acetone and thinner

  3. Applied the adhesion promoter

  4. Applied two layers of flexible primer

  5. Flatted the primer obviously: that primer is super hard, incredible

  6. Applied two layers of base coat

  7. Applied two layers of clear coat

  8. Got really very pleased with the result

The finished product

In retrospect, I should have put the stickers under the clear coat. But there is always time to add a couple of layers of clear coat later.

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While I was at it...

I also did the front headlight shroud and the side panels while I was at it..

Let's put it to work

After 100 miles in the Mexican desert, the black marks on the side are wear from my pants. These came off nicely with 1200 wet paper. There is still plenty of lacquer left on the tank. Finished with polish and buffing. Very easy. I had the replace the stickers that were worn out.
The bike remained parked for 4 weeks after the race with 110 octane fuel in the tank, no sign of bubbling.
A great success but wasn't cheap or fast...

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An important usage update

After 8 weeks of keeping fuel inside the tank,... bubbles started to appear. Obviously, fuel vapors found their way through the liner and the plastic to the paint job. I popped the bubbles with a small pin and pressed them back flat. Since then I always empty the tank and leave it to air between rides. So in conclusion, it is a half success...

One year later:

After The paint is holding very well, no problems there. Inside however, the liner has come off the plastic walls. It is now a very hard shell replicating the shape of the tank, only a few millimeters smaller than the tank. Not good, but I will probably just leave it as is.

Celebrity advice

February 2015

In a Facebook thread about plastic tanks, Mr Preston Petty himself informed me that this tank is a "cross-linked polyethylene roto-molded plastic" item. There! I like to know what things are made off, this is great info.

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