HOW TO: Repair plastic side covers

I've been experimenting with different ways to repair the plastic side covers for a couple of years now. I have now refined the technique to the point where I can share it, but note that it may continue to evolve in the future.

When you go out and start searching the internet for guidance on repairing plastic side panels, there isn't too much to be found. You probably end up with the guy who uses super glue and baking soda to build up and shape a peg - it may be a perfectly good repair, I don't know, but it didn't strike me as a method I wanted to learn to perfect.

Part One: Repairing a Broken/Missing Tab
In this first installment, I will go through repairing a broken tab. This is, of course, a common problem, and the good news is that it can usually be repaired without requiring refinishing of the panel - just add a new tab and off you go.

Materials required:
1. Mold making putty
2. JB Weld Plastic Bond
3. Sheet of carbon fiber (fiberglass mesh tape might work too, TBD)
4. Mold release spray


The JB Weld Plastic Bond is a two-part urethane system. It maintains a bit of plastic-like flexibility, unlike a lot of epoxies that will end up rock hard. This is my current go-to after trying several different options. Admittedly, I never tried super glue and baking soda.

The carbon fiber is used to create some mechanical structure within the repair. Unfortunately, cutting the carbon fiber sheets into a piece small enough to make things like the tabs is pretty much impossible, so we will end up embedding individual strips of the carbon fiber one-by-one in order to make a good mesh inside the repair. Embedding carbon fiber may not be an absolute requirement, but it's how I do it.

For this how to, I will be repairing the left side panel that came with my XJ650RJ. It has one broken tab. Luckily it is the left side panel, so I was able to acquire an intact left side panel from eBay to use as a model without breaking the bank.


Following the directions of the mold making putty, I created a mold from my model.


Now I am going to clean up the area that will end up with plastic bond applied to it with lacquer thinner (or acetone). Next, using some sandpaper and a rotary tool, I want to rough up the surface where the plastic bond will end up inside the panel. I also want to make an angle where the tab is broken so that it is not just an abrupt 90 degree edge. We will want an angle in order to smoothly run carbon fiber strips from the inside of the cover down into the rebuilt tab area.

Apply some mold release to the mold and then put the mold on the part that needs repair.


Mix up some plastic bond, and apply enough to be able to embed carbon fiber strips into. Carefully embed some carbon fiber strips into the repair area. Ideally, you want to end up with a criss-cross sort of pattern. I use a toothpick to kind of smoosh it into the plastic bond.


The plastic bond says that it has a 15 minute set-up time and sandable in 30 minutes. In my basement, I have at least 15 minutes of work time, probably more. My basement is usually around 65 degrees F, so it may be a different story in New Delhi in July. At any rate, it's plenty of time to get the carbon fiber added. It also says sandable in 30 minutes. I have found that it needs at least overnight to cure, usually more like 24 hours.

Now I finish filling the mold and cover the carbon fiber with more plastic bond and let it sit and cure.


After curing, I can remove the mold - and there we have a new tab! Once the plastic mold is sufficiently cured, it can be sanded to make it look nicer and primed and painted if needed.


In this case the finish on the rest of the panel is garbage, and the panel will need to be refinished. However, you can see that if the finish was good to begin with, I could have avoided sanding, then this panel would be perfectly usable without any further refinishing.


Broken pegs can be repaired in much the same manner. However, instead of carbon fiber, I prefer to use a thick wire as the core structural material. Next time I do one I will try to make a follow-on post.

 

Part Two: Panel Bodies

The repair of the plastic side cover / battery cover panel bodies themselves is possible too. And any other plastic body panel for that matter. It will be very familiar to anyone who has ever repaired a plastic bumper cover or something like that. It is basically body work on a small scale. However, since it is like body work and any imperfections will be seen when painted, you need to be extra patient and careful to make sure it is done right and you won't end up seing flaws after painting.

For this part of the series, I will be repairing this panel that is... well... there's no nice way to say it. It is $#!+housed.


This is a 1980 XJ650G/1981 XJ650H Maxim right side cover panel. This is identified by the two holes in the panel where the emblem mounts. On the 1982 XJ650J/1983 XJ650K models the emblem was glued on, so they didn't have the two emblem mounting holes. It is pretty easy to convert a G/H panel to a J/K panel, and vice versa - just drill or fill.

This particular panel was originally black. It was painted red at some point.

The more I looked at this panel the more cracks I found. At first I thought it was just the obvious damage. Turns out there was a crack towards the top left of the panel and the area above the tabs was cracked too. Not sure what happened to this panel. Maybe the bike was laying on its side and somebody stepped on it. Maybe it had an encounter with a goose at 80 MPH. I don't know. It is bad. But not beyond repair. On the plus side, all of the tabs and the peg are intact.

Plastic can stretch and be deformed when it breaks or cracks. Sometimes you will need to use a rotary tool to trim up the edges so that everything will fit back together. It is also good to clean up the edges in order for the epoxy to get a good bond. Here is the panel after cleaning up the edges and making sure everything fits back together:


In addition to cleaning up the edges and making them fit, it is good to put a little taper on them too so that the epoxy forms a mechanical connection, sort of like this:


In theory, pushing on the repair (the red epoxy in the diagram) up or down will be counteracted with a mechanical force, not just the glue bond between the panel and the repair, making seams much stronger.

The first thing I will do is to glue the perimeter together and make sure everything lines up correctly. Here I have the panel clamped together, with some popsicle sticks on the outside to hold everything straight.


Add some bonding material (glue):


Then right away embed some carbon fiber to give it strength.


After 24 hours of letting the initial repair cure, the broken piece can be positioned and held in place with some masking tape.


Then do the glue and fiber procedure on the inside of the broken piece:


One more crack to fix on the top:


I found some more cracking on the side by that tabs:


Now I'm using the bonding material to fill in cracks on the exterior. Basically using the bonding material as a body filler:


Of course the shaping of the part, like most bodywork, is part art and part science.

After some shaping, just a final skim coat:

 

Part Two: Panel Bodies (continued)

Here is the panel with the repair work and shaping completed.


Now on to primer. This will fill in and smooth any small imperfections and sand scratches. Then it will be ready for final finishing.

 

nice work! I am inspired to make a proper job of my damaged side panels this winter.

 

Nice work....well done.

I have been playing with PVC welding with a soldering iron and good ventilation. That has been working well too.

 

Had to repair a lot of plastic bits on my XJ750 seca - I used a fibre-reinforced body filler (used similar to ordinary body filler, except it is a thickened resin with chopped fibre glass in it)
My issue is areas under stress seem to flex enough that my paint actually cracks on the ductail near the tail light. it hasn't been repaired, but it seems to have a range of flex cracks that only show up on painting.
Have you seen that tourself?

TTFN
Clint

 

Excellent how to thread.

 

This is excellent info! Looks like an older post, so I'm glad it got bumped back to the front. I've tried similar small repairs with ABS plumbing glue with some success, but never on something "structural" like the side cover snap clamp. The JB Weld plastic stuff really looks like the ticket.