Vintage Dirt Bike Q & A

I am restoring a 1980 cr250r which has the plastic gas tank. The tank is functional but of course the color is faded with time. Has anyone had any luck refinishing the plastic tank with new paint? I know plastic has some major challenges with painting. What color and prepping techniques work best?
Thanks.

I think you will be better of polishing the tank instead of painting it.

Thanks for the feedback. I believe you are right I can only find mixed results with folks who have tried to paint and often the tank ends up looking worse. I have worked on the tank with wet sanding and it's starting to look better so I believe I'll stay on that route. Some have said wet sanding with a few coats of Maxima SC1 plastic wax really helps.

Don't use paint.

OK, after you don't paint it, polishing is the best route. I did my '80 CR250 tank and '85 CR125 tank this way:

1. remove all stickers and petcock assembly.

2. using a single blade razor blade, scrape the white chaulky stuff off. Go slow as not to gouge the plastic.

3. start with 400 wet or dry. Do the whole tank to an even dull color. If there are dark spots, they are on the inside & usually don't come out.

4. repeat #3 with 600, 800, 1000 and 1500.

5. do a final sandinging with 2000 grit. Each of these "sandings" will produce a white chaulky liquid. This is the dead pigment/plastic. Be sure to do this all by hand so as no to thin out the plastic.

6. Last step - polish at LOW speed with a buffer. Do not use an angle grinder, will burn the plastic. Start with a light compound and see where you are at first (test panel). It you follow the sanding steps should be looking quite nice. Follow up with a motorcycle windshield polish for the final polish.

NOTE: stickers will not stick to the plastic due to out gassing of fuel. If you still want the Honda wings, perforate them with a small leather punch. They still are gonna bubble, but not as quickly.

The other possibility is to use a 78/79 tank.

GSJimmy,
Thanks for the tips. Good to hear from someone who has had some luck. You mentioned polishing with a light compound so I'm curious what you used?
Thanks.

I used 3M products. Any autobody supply house can set you up. Started with a light compound and added in a bit of 3M heavy compound to remove some of the stubborn areas. Go real slow with the buffer so you don't burn the plastic. Used a wool pad first.

Once an even shine is obtained, go to just a light compound (repeat above).

Then I followed up with a product called Race Glaze. Has some wax and a very fine grit in it. Switch to a foam pad at this point and increase the buffer speed just a little bit. You may want to mount the tank on the frame to make it easier to hold onto. Be sure to cover everything you don't want compound on (stuff really flys!).

With the Race Glaze you can rub out small areas by hand with decent results. My '80 CR250 had a lot of chaulking and some deep scratches that I covered with Fox Air tank decals (after using a punch to perforate to release gases). Worked fine for a track bike.

If you can't find Race Glaze, motorcycle windshield polish will also work.

Jim

I finished the tank and I'm pleased with the results. I hand sanded all the way through 2000 grit then put several coats of maxima sc1 polish on by hand and the tank looks really good now. There are a few scratches that I suppose I will just leave as it will no doubt add character. I may look into the Fox decals you mentioned and I will add the new wings later.
Thanks for the feedback.

Make sure you drain the gas out of the tank after each ride and leave the cap off so the fumes don't bubble your decals. It's a little more work but it will preserve your decals. No need to punch holes in the decals with this method.

Good tip - mine ended up bubbling anyway.