THE BODGER`S GUIDE TO PLASTIC POLISHING
If you had asked me fifteen or so years ago if it was possible to take a badly sun bleached plastic mudguard from a dirt bike & polish it back to somewhere near a presentable condition, i would have said no. As far as i was concerned it would only have been fit for the bin. Time to find a good used one or buy new. Luckily for the vintage dirt bike owner times have changed & thanks to the very thing you are using right now “the internet” information gets passed around & today plastic body parts that would have once upon a time become scrap can now live on.
As the title of this article suggests “Bodger`s Guide” i am no expert in this subject & if you have a very rare bit of plastic that is incredibly difficult to replace then it might be wise to seek the help of a professional. No doubt they will charge handsomely for their services & talk the job up. They will explain how there are many different types of plastic used in the manufacture of mudguards, fuel tanks, side panels & radiator shrouds. Japanese companies use this type, European companies may tend to use another. Each type of plastic may require different polishing methods, some may not respond very well to polishing & not really be savable what ever you do. NOTE if you do decide to have a go yourself at polishing a fuel tank then please take all necessary safety precautions & please don`t blame me if you happen to set your own face on fire !!
Presuming you have something that can be easily replaced if you do make a complete hash of it such as a rear mudguard from a 1991 RM 250 as shown in the photos then have a go. As you can see this really was pretty awful & i didn’t have much to loose if all went wrong. The areas where the stickers had protected the plastic from the California sun were now raised & sat well above the rest of sun bleached & very crumbly plastic surface. My own personal goal was to get this mudguard back to a usable & presentable appearance so that from six feet away in the paddock the item looked OK. You can of course spend many many more hours than i did & sometimes get things back to as new condition but i ride & race dirt bikes, i just need something that looks tidy, i will no doubt be throwing it down the track in the near future. If you rebuild bikes to be show ponies & the plastic needs to be mint then you will be a very very busy boy or girl indeed. If not careful you can end up creating far more & even deeper scratches than you started with so go steady & be very gentle if you are aiming for a top quality finish.
Right from the off i hit this piece of scrap plastic with a combination of very coarse grit sand paper, sometimes by hand, sometimes mounted on a normal type DIY Black n Decker orbital sander & a scraper blade. It was then just a case of gradually working my way down through finer grades of sandpaper & wet n dry until i decided it was time to attack it with ever finer grades of rubbing compound, T-Cut, car polish etc. If you have a proper electric car polisher, they rotate a lot slower than a drill or angle grinder, give it a go over with a soft foam or lambs wool polishing mop attachment & some polish. Keep the mop wet with a bit of water from a spray bottle & keep it moving around so you don`t burn up the plastic in one spot.
Yes if you held the mudguard up to the light & looked very closely you could still see a faint outline of where the raised DUNLOP stickers had been. Yes there were still some scratches to be seen but i think you will agree that once the whole piece had been given the same treatment it would look OK from six feet away in the paddock & that was my original goal. Not a bad way to spend a couple of hours while listening to the radio in the workshop. Have some fun, save a bit of cash & i will see you on the start line. Mr J classicdirtbikerider.com.