Painting motorcycle parts 

Spray paints that you can buy in the shops are either acrylic or synthetic resin-based. Modern automotive spray paints are almost exclusively acrylic-based, while hobby spray paints (and, of course, brushing paints) from DIY stores may also use a synthetic resin-based formula.

(automotive paints) offer the following advantages:

• Quick drying (touch-dry in 10–30 minutes)
• Recoating possible any time (whereas for synthetic resin paints: within 2 hrs or after 24 hrs)
• Better corrosion protection
• Greater resistance to cleaners; harder surface finish

Synthetic resin paints, however, have better filling properties and often spread more homogeneously over larger areas. They're less expensive than acrylic paints, and are popular for hobby and craft use, but they are less suitable for painting motorbike parts.

As well as the popular single-component paints, two-component paints are also available in spray cans. They are harder wearing. Clear lacquer, for example, is ideal for overcoating normal single-component automotive sprays to create a high-gloss finish with greater resistance to scratching, petrol, and weathering. And if you're after a special shade, automotive paint retailers offer a huge range of original colours, which they will mix for you and put in a spray can. However, we recommend finishing these paints with a top coat of two-component clear lacquer. For further details on the best method of application, ask your local specialist retailer.

The primary function of paintwork is to protect against corrosion. To achieve this, it's essential to first mechanically eradicate all traces of rust. For this job you can use coarse sandpaper and wire brush attachments for your power drill or angle grinder. Sandpaper is good for removing surface corrosion, and wire brushes for power tools are then able to penetrate deeper into the rust pockets, helping to eradicate them completely. The deeper the rust goes, the harder it is to remove all traces. If you feel you've done all you can with your wire brushes and you can still see rust, apply a rust converter (follow the instructions for use on the packaging). Your only other alternative is to take the part to a specialist workshop that does sand or glass bead blasting – it goes without saying that this method is best of all.

Dented, uneven surfaces can be repaired with a two-component filler.

Large dents can be gently hammered or pressed out using a rubber mallet so that you don't have to apply the filler too thickly.

You can repair any rust holes by welding, or by bridging them with glass fibre mats or a two-component product containing glass fibres.

Mix the filler on a largish surface following the instructions on the packaging, and take extra care to avoid air pockets during application, as these would result in bumps in the filled area later, or even cause the filler to come away!

The surface must be absolutely free of grease and dirt, so you should clean the whole area extremely thoroughly using silicone remover, thinners or brake cleaner! Once the filler has hardened, sand it down until you have a smooth finish. To do this, wrap a piece of wet sandpaper (approx. 100–240 grit) around a sanding block or a piece of wood (if you don't use a sanding block you can easily end up with slight depressions on large surfaces). Only small repairs on curved surfaces are best sanded without a block. When sanding curved surfaces, always follow the shape of the part so that you don't end up with flat areas or depressions.

Wet sanding will keep the dust down considerably while you work. After sanding, you should dry and clean the surface, then run your finger tip over it to see if it feels smooth. If it's not 100%, degrease again, apply some more filler and then sand down again. Any remaining fine pores and/or minor grooves can be filled using fine or spray putty.

Now you can finally start painting. Never apply the top coat straight onto the substrate – nor straight onto the original paintwork (the only exception is if you've already used the same spray top coat before or you're painting an engine with thermal paint), as it would easily peel off. Apart from which, the top coat on its own doesn't offer the required corrosion protection. If you're painting over original paintwork, first sand down with a 400 grit wet sandpaper, clean thoroughly with silicone remover and then spray on a primer or filler.

This promotes adhesion of the top coat and fills any minor sanding marks. High-quality two-component primer fillers produce outstanding adhesion and particularly hard-wearing paintwork. You will have to dig a bit deeper in your pocket but the reward will be a very professional result.

When the primer has dried properly, smooth down with 600 grit sandpaper, making sure to remove any dust inclusions and imperfections. Carefully remove any loose dust from the surface (using a lint-free cloth or special "tack cloth" from a specialist retailer). Do not touch the surface to avoid leaving traces of grease from your skin!! If necessary, degrease by wiping with silicone remover, but do not use thinners, which would dissolve the base coat.

Now apply the top coat. As previously described, apply a mist coat and then 2 or 3 crosswise covering coats, avoiding drips (see Step 4). If you see a drip forming, you may with a bit of luck be able to smooth it out by turning the part around. 

If you're doing a two-tone paint job (see Step 7, Fig. 2), allow the first top coat to dry at least overnight, then mask it off ready for the second colour using a special curve masking tape from a specialist paint supplier (see Step 7, Fig.1). This tape is ideal for applying around curved surfaces on your bike's bodywork. On removal, it gives a clean edge and doesn't leave any adhesive residue on the surface. Do not use normal masking tape, as you will end up with rough edges! Fine-sand the surface and remove any spray mist that lands on the first top coat.

If you're using a metallic paint, let it dry for approx. 30 mins (or longer) and then apply a clear lacquer to protect it against weathering and to achieve a mirror finish. Non-metallic paints also have a more attractive high-gloss appearance and better protection if you apply a final clear coat, preferably a two-component lacquer.

If the paint surface is not completely smooth and free of spray mist, give it a final finish after a few days' drying time. Smooth away any larger imperfections using 1000 grit wet sandpaper. Fine spray mist and the sanded area are then fine-polished with a special polishing paste. This will produce a beautiful, smooth finish that looks as good as the original paintwork. However, single-component paint is always slightly less hard-wearing – so try to avoid scratches and always avoid dripping any DOT 4 brake fluid. The paint is theoretically petrol-resistant, but petrol spillage does tend to leave the paintwork matt, so it will need to be buffed up again. Finally, protect the paint by applying a layer of hard wax to seal it and ensure a lasting shine.