How to fill and repair scuffed plastics

Scuffed, scratched, crash-damaged plastics are the bane of many 1980s and ’90s sportsbike owners. With NOS panels either unavailable or hugely expensive, repair is often the only way. Here’s how…

y Yamaha RD125LC’s nose fairing is typical of many ’80s and ’90s sportsbikes’ plastics. An over-exuberant former owner slung the RD up the road leaving the fairing covered in deep, ugly scratches. It looks a mess on the bike, so was resigned to a life in the loft thereafter.

Repairing it, though, is relatively easy, doesn’t take long, and is a far superior option to buying a cheapo glassfibre replica or a ludicrously priced NOS item. 

With the help of PS friend and seasoned restorer, Gary Haythorn, we’re going to repair the damaged fairing and get it ready for priming.

TOOLS FOR THE JOB

You’ll need: three grades of sand paper (40/80/180). The amount you use will depend on the size of the area you’re dressing; a sanding block; filler, hardener and a spreader; a heat gun or hairdryer, a screwdriver and spanner to remove any panel ancillaries.
A dust mask and goggles will keep any dust/fumes out of your eyes and lungs.

Techinal level  3/5

Time taken  1.5 hours

Cost  The only real cost you’re looking at is for the filler, hardener, sandpaper and possibly a sanding block. We used U-Pol Easy 1 filler and T Filler hardener which comes as a kit (3.5 litres of filler, two tubes of hardener and a spreader for around £25). Sandpaper will cost a couple of quid all in, and sanding blocks can be had for a couple of quid. In total you’re looking at around £35.

 

1. Remove all unnecessary trim from the panel you’re working on to prevent it getting damaged. In this case, with a fairing, take off the screen, the bead trim that runs around the fairing’s outer edge, and the internal mounting brackets.

 

 

 

2. We want to apply the filler to a clean surface, so remove the decals. Factory decals stick like limpets so they’ll require heat to shift them. A hairdryer will do if you don’t have a heat gun – apply heat to one of the decal’s solid edges, then slowly peel it away.

 

 

3. This fairing is a mess, with deep scratches and spikes of impact-melted plastic. We need the area to be flattened and keyed so the filler can find purchase. Rub down with a rough grade paper (P80) to remove the worst. Blow particles away with an airline/hairdryer.

 

4. Mix the filler. We’re using U-Pol Easy 1 filler and T Filler hardener (they come in a kit with a spreader). Mix filler with hardener at 50:1 or, as Gary says, a golfball size of filler to a pea size of hardener. Mix with the spreader until it achieves a uniform colour and consistency.

 

 

 

5. Now you’ll need to work swiftly. Once mixed, the filler and hardener begin a reaction that renders the mix useless after roughly five minutes. Apply the filler in small amounts at first. You want a 5-6mm covering over the worst areas so you can sand it down into the desired shape.

 

 

 

6. The filler will harden fully after 20-25 minutes. When it’s set, rub it down with a 40-grade paper and a sanding block. Don’t apply too much pressure to begin with – 40-grade paper is harsh enough to rip the filler. Work gently until the area is flattened off.

 

 

7. Once you’ve taken the rough edges off the filler with 40-grade paper, switch to a finer 80-grade. Fairing panels have very few completely flat surfaces, so you can create the curves by working the front or side edge of the sanding block into the filler to form the desired shape.

 

 

8. Use the other side of the fairing, or its opposing panel, as a guide to shape. Feel the angle changes with the tips of your fingers and compare them with the area you’re shaping. Don’t panic if you end up removing too much filler though – you can always add more to correct mistakes.

 

 

9. When you’re satisfied that the shape of the filler matches that of the original fairing, finish off by rubbing it over with P180 paper. This will remove any large scratches from the filler and enable you to feather the edges of the filler into the surrounding surface.

 

 

10. Once you’ve smoothed the filler down, blast the fairing with air to remove any dust. Then key the rest of the fairing/panel with Scotchbrite in preparation for the application of primer.

 

 

 

11. Nosecone now ready for priming. Next month we’ll show you the best way to apply primer to provide a good base for a smooth, consistent finish. A little preparation now saves hours of remedial work when we get to the top coats.

 

 

Words Jim Moore  Photography Rory Game