by (Mark Wurtzel)
VFR (and most other Japanese bikes) use ABS panels. The fender and seat cowl are of another plastic I have not yet identified. Fiberglass resin (polyester or vinylester) and glass fiber cloth or matt will not effectuate long term repairs on ABS. If you rough the surface up (like with 60 grit sandpaper) they may have a bit of mechanical grip but you still will only have nominal chemical bonding.
IMHO there are really only two ways to do a 'proper' (i.e. permanent, not detectable repair) repair of ABS. 1) plastic welding using the proper rod. VFR's are 100% ABS, Some newer Hondas (including '90 & up VFRs) & many Yamahas use, IIFR, HDPE front fenders. They are quite easy to ID - sort of milky white with a waxy feel as opposed to the very rigid fell of ABS. You must use a rod of the same material. In my experience I've never come across any motorcycle bodies made of any other plastics.
Reinforced fibers (fiberglass, carbon, Kevlar) are quite easy to ID due to the fabric & each must be repaird in a different manner, though they can be repaired with a basic Home Depot fiberglass repair kit, you will certainly sacrifice structural
integrity if using this technique with the aramid fibers.
The pros of plastic welding are the repaired structure will be as strong as it was prior to damage, the welds can be ground smooth (inside and out) so there is no evidence of repair. The biggest con is that is very, very difficult to do it to a painted panel without burning at least a bit of the paint surrounding the damaged area. Obviously, if you plan to repaint the panel, this is not an issue. I have seen plastic welding done (by a very talented friend) whereby the paint was not damaged. But I certainly cannot do this and most people I've spoke with who are far more experienced plastic welders than me assure me it cannot be done (!!) -So I wouldn't plan on being able to do this!!
2) The other method is to use an ABS adhesive, such as you would find at an autobody supply house. One of the better products is made by Polymer Engineering Corporation under the Duramix brand. I believe they sell only through professional outlets but their phone number is (800) 537-9204. The product I have used is #4039 in a small double syringe like dispenser.
The pros of this are you don't need a plastic welder (duh!) and it will not burn the paint. You can get a pretty good repair by just gluing the panel together with this product and sort of laying a wider bead on the backside of the panel & reinforcing with a special cloth. To really do it right, you need to grind and patch both sides, which of course will necessitate repainting.
You can try using a generic epoxy and may or may not have good results. I've known friends who have had this work for several years and others where it hasn't lasted more than an hour. I suspect the chemistry of the actual adhesive
as well as the amount of stress on the part in question both contribute to this disparity.
Regardless of what method you are using I'd use a good grease & wax remover, which you can get at your autobody supply house. Alcohol is not bad, but the grease and wax remover will probably give you a better result.
I guess a lot of this will depending on the specific type of damage (i.e.: is the area heavily stressed) and how much you care about the look of the final product and if you are trying to avoid repainting.
Either method will work satisfactorily for reconstructing missing tabs and the like.
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