When considering whether or not a panel is worth repairing you need to take a number of things into account: Paint, decals, age and in some cases the foam backing.
Some manufacturers stick foam to the back of their side panels to stop the engine/frame
work rubbing against the back of the faring. It also stops any knocking noises and vibration while the bike is being ridden. When a panel sustains damage resulting in a crack or breakage or both, it does not always transfer to the foam behind. Even if it has not, the foam needs to be removed to do a repair. Where plastic welding is used the heat from the machine will melt the foam giving of a noxious gas. In most cases we can separate the foam in one piece from the plastic panel. So it can be reattached after the repair is compete, there by saving the cost of new foam for the customer.
There are some situations where it can not be removed in one piece. Foam, like plastic, deteriorates with age but at a faster rate. There are two types of foam backing – open cell and sealed. The former gets impregnated with road dirt, oil etc, this helps to degrade the backing more quickly turning it to dust, making it impossible to remove in some cases. Because the later is sealed it repels most of the detritus thrown up from the road and stops oil soaking into it. This increases the life of the foam, therefore making it a better candidate for removal when a repair is needed. The sealing helps to keep it in one piece making it easier to remove.
The pictures show.
Thunder cat side panel. One with the foam mat partly removed.
We do from time to time get asked to repair plastic on bikes that are more than thirty years old. These panels present some unique challenges. Panels made of ABS, age, this leads to deterioration that shows it’s self in a couple of ways. The first are fishers appearing in the panel as you pass heat over the area to be repaired and secondly moisture leaching from these hair line cracks. It is well known that untreated ABS is hydroscopic.
Recently we had a gent in with two very old Triumph battery covers that had stress cracks. I say stress but to be honest these were signs of their age. The next indication was the way little rivers of water came running out of the plastic as heat was passed over the repair area, with numerous fishers opening as well. This complication turned a straight forward repair into a bit of a challenge.
It is difficult to know how far to to take repair’s like this. It was handy that the owner was in the workshop to experience what was happening. We agreed between us to only make good the cracks and some of the fishers that lead into those creaks. Otherwise the repair would have become very expensive.
We are often asked to repair plastic petrol tanks and motorcycle windscreens. In the case of the former we say no even though we have in the past repaired one. We only did it as an experiment to see if it could be done and the customer had spare tank material we could use to plug the holes. Did it work? As far as we know; we tested it with water in the workshop with no leak but petrol is another matter. We are happy to try another as a test to see if it works or not. BUT the material has to be identical to the tank you want repaired.
As for motorcycle windscreens we can repair them as long as they are made from Polycarbonate and the crack or piece broken off can not be seen when repaired. There is nowhere to hide with clear materials as you can see from the picture. Once repaired and prepared the plastic go’s a milky colour. Imagine how that would look running down the middle of your screen.
On a more serious note, in some cases broken screens are less expensive to replace than have repaired.
Even though plastic welding has been around since the seventies it is still surprising when a faring from that era comes in, how much fibre glass has been used to patch up the damaged areas. We were asked if it was possible to repair the plastic panel on a GSX 750 Katana the one with the pop up head light.
From what I have already said you would have gathered that these panels were in a bit of a state. Of all the farings that turned up it was the left and right side nose panels
( the nose cone in this case is divided into three section two sides and a Bezel that fitted around the pop up head light) that presented the biggest challenge. The customer wisely turned up with two panels for each side. The problem was to work out how much of each panel was the original plastic and which pair had the least fibre glass holding it together.
Fortunately the headlight bezel only had a cross shape lug missing. In itself not a difficult repair
but time consuming to reproduce. All the side panels were heavily damaged where the side mirrors would be mounted. One of which had a big bit missing.
The first thing that needed to be done was to get rid of the large quantity of fibre glass from the damaged areas.
Once it had been ground off the outside of the panel. The stuff caked over the inside was gently persuaded to leave home, coming away in one piece. Almost leaving it clean enough to weld. It just go’s to show if it had not been fibre glass both sides it would have fallen out ages ago.
The one thing plastic welding does not like is contamination of any kind. Which meant we had to remove as much of the residue as possible to be sure it would repair properly.
Once that was done new plastic was cut into shapes to replace all the missing bits. Because alot of the damage was concentrated in one place we had to be careful about over heating. By phasing the repair it would keep the heat shrink to a minimum, making for a better repair over all. You also have to take into account when renovating old plastic it has a tendency to get very brittle. A way round it is to temper the area with some heat before you start welding it together. This also helps to drive out any water that the plastic has soaked up over the years. This leads to a stronger weld and a satisfied customer.
Not all the plastic that turns up at our door can be repaired by gas welding. Dare I say it that we have to resort to two pack bonding don’t get me wrong it is a good repair but 90 seconds to apply the adhesive is not on some occasions enough time to get the job done.
The other day I had to nip out to get some materials. A bit of an under statement as it involved a journey of a hundred miles each way. As we were going up the by pass at the beginning of the trip there was a metallic clanging sound of something hitting the under side of the truck which slowed progress as I considered whether or not to stop and check. Needless to say I didn’t as the van felt and ran OK.
Ninety odd miles later . We stopped at a well known supermarket for a break. To be met by a shushing noise. A quick look round the truck did not show anything untoward but the shh persisted; then I noticed that the rear near side tyre looked soft. In that short time it was half flat, the air was coming out that fast. I can’t believe it – another puncture! and its the new one! I will not repeat what was said but I think you can guess!
I ran round to the cab pulled out the jacking kit and got it in place just before it went completely flat. Ten minutes later the Tyre was changed.
Before we returned home I wanted the puncture repaired, so tracked down a tyre shop and took it in. “No prob’ mate have that done for you in a jiffy”. Then things went sideways I saw him call over a colleague and then me. It took us all by surprise. I was told that I had been extremely lucky that it had not blown apart when it happened. The pictures speak for them selves!
5. Ground off plastic from bikes that have slide down the road.
We rebuild these with plastic not filler.
6. Panel support mounts.
7. Making mount post from scratch.
8. Broken panels.
9. Missing part taken from a donor panel.
10. Small parts made from scratch.
When we had the idea to do this everyone thought it was great. The reality is that we could not agree in what order they should be placed or if we had the images required to make the top ten. It would be fair to say that these are the most common repairs we see and to a certain degree can be complicated to complete.