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Discussion Starter #1
Over in my TR7RV restoration diary I mentioned that I was trying to restore the plastic air filter covers.

I bought this:

I've used the ali and chrome versions of this with mops on my bench grinder very successfully, but not had much success with the plastic.

They are the '73 on covers, so without the flutes, just a plain surface. I can buy repro covers cheaply enough, but I would like to get the originals back to be near the quality of the powder coated side panels.

The covers are fine structurally, no cracks or significant gouges. They do seem to have a streaky pale grey 'stain' to them - which I think is oxidation. The plastic polishing kit does work to a point in that it will produce a shine, but there's still the grey streaky marking to get rid of.

I suspect I need to sand back (wet and dry) the covers to a clean plastic, with say 380 and then 800 grit, before trying polishing again.

I did give them a good sanding with 800 grit, then thoroughly cleaned with acetone before trying plastic paint. Useless. the paint rapidly crept away from numerous points to leave a surface reminiscent of the surface of the moon. I suspect, that no matter how much I clean them, there are very small point sources of oil accumulated in tiny pores over many years. Painting isn't going to work.

Anyone done this before and if so did you get a good finish? Given the amount of work involved, I may be better off cutting my losses and buying new, but I would like to keep the originals if I can. Any ideas?
 

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Hi Andy, Do they still fit tightly around the alloy housings? Air leaks, gaps around edges is a serious problem with these. They tend to warp in many ways & areas.

Hard to tell how deep the grey goes. Fine wet/dry used wet can help. Finally buffing to shine like you think. Depending on black you painted tin covers it may never match. different shades of black. I find Kylon Gloss black is a good match.

You could try painting covers also. Specific gloss black for plastic paints are made. Call some auto body supply shops if needed.
Sadly there was a rumor floating around some years ago about aftermarket alloy smooth covers. I could never find a listing. I doubt they ever existed.
Don
 

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Discussion Starter #3
Hi Don, I've tried painting but I think there's so much very small spot oil contamination It's not going to work. Polishing is my only option, unless someone knows different. I just need to work out how to get that polished finish with the kit I've got.

They do seem to fit well, and they are fairly undamaged, no cracks, splits, bits missing or gouges. If I could make them look something like I'll re-use them. I'll accept they'll never match the new glossy black powder coat on the metal side panels, but hey, this is a rider not a no-oil-or-pistons museum piece.
 

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What about finding some alloy covers and either having them powdercoated to match, or if possible, sand/machine off the flutes or even fill if the flutes are lower/deeper than the base?
You could use the fluted ones and mask off the fluting as a contrast?
 

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I had the same problem. I ended up sanding them down to the plastic, using JB Weld to fill any pitted places, priming them and then shooting a coat of base coat and clear coat on them. Then I buffed them out and they look like new.
 

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Acetone as a panel wipe probably was not the best idea. If you want to paint them you will need to use an adhesion promoter before applying a filler primer.

Rod
 

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Discussion Starter #8
Hi Redmoggy, I used a Rustoleum paint product, for direct to plastic, no primer required. I'm convinced the paint didn't apply well because there's muck in the moulding that I can't shift.

I have just tried polishing the seat catch knob, with some success. I used the finest of the 3 waxes I bought, and the finest mop, and that seemed to work - hadn't previously tried these 2 parts of the kit. Got quite a good finish, much better than when I used the other 2 waxes (coarser) and their mops. I think the filter covers will polish up, I just need to work out how to do it.
 

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I would be inclined to think that your issue was the acetone. Acetone is an aggressive solvent that will remove most paint finishes, it will also attack plastics. My guess would be some of that acetone got a good bite into the your freshly sanded surface and remained long enough to react with your paint. I've done a few plastic and GRP covers and they really only require scrub with hot soapy water. Use of an actual panel wipe solvent will remove oil left over from skin, waxes etc.

Rod
 

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Discussion Starter #10
Hi Rod,

That's interesting. I'll try again and this time use some panel wipes, or some cellulose thinners maybe - I have plenty of that.

I've plenty of isopropyl alcohol too - that seems to be the ingredient of panel wipes.

Many thx for the tip.
 
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