Pinned Repairing cracked and broken ABS Fairing's, plastic welding

This is my right side fairing off my '90 FZR250, there is a piece missing and a crack that run's up from the corner of the missing section.
I am repairing it by plastic welding, using a 20w soldering iron with a broad flat tip (also used for craft / woodburning)
Using a soldering iron with a too high wattage will cause the ABS to bubble and leave you with lot's of air pocket's which will show up when doing a final sand
There are quite a few different way's to repair plastic using specialist tool's and adhesive's etc, but they can cost quite a bit.
This method is one of the cheaper way's of doing it yourself.






The fairing has been repaired previously but someone who has tried to fibreglass it back together
Fibreglass can be used as a temporary repair, but usually the glass and resin end's up with an unstable bond, if you flex the join it will come apart




I bought a small pack of ABS welding rod's from my local hardware store (Bunning's, cost $11.60)
And went and saw a local Plastic's Fabricator and he gave me a small offcut of flat 3mm ABS sheet.
The black piece here




The tool's i used were a Hobby/Craft soldering iron, with a broad flat pointed tip.
A sharp Olfa Knife for cutting the ABS, and a hard sanding block with decent (3M, Norton, or Carborundum) 80 grit and 180 grit freecut dry sandpaper, some 320 grit 3M W&D paper and a soft block for final rubbing back once primed
My soldering iron is a Black and Decker 20w craft model, it came with an assortment of tip's.
You might be able to modify an old soldering iron tip by flattening it out with a hammer to give it a similar shape.
I also used a small Butane Gas Torch to help me bend the ABS sheet
















First thing to do is to clean up the fairing where you want to repair it.
I needed to remove the fibreglass patch's and sand back the dried resin remain's, and sand back the remove the sticker's and black paint on the outside
Once this was done i put the sheet of ABS into a vice to bend it, i heated it evenly with my Butane Torch and folded the 90° bend into it.
While it was still soft i clamped a piece of steel down on top to help it keep the new shape.
It take's about a minute to cool, and is very easy to work with.








Next i marked the ABS with my Olfa knife slightly larger than what i needed and cut out the triangle section
I ran the blade across the plastic firmly a couple of time's then snapped off the triangle





Next i filed back the new piece with the sandpaper and block to get it to the size i needed.
I used some gaffer tape on the outside to hold the new piece in place while i started to weld it.
Push the tip into the plastic and move it forward a touch to let each side of the join pool together in the middle of the weld, then move onto the next
This give the ABS a firm hold together, make sure the part's sit flush on the outside, or have the new piece slightly proud of the surface to allow for sanding it back flush later.










Next i cut some bit's of rod to melt over the stitching and join it together
I heat up the ABS bit's with the iron then press them into the plastic to fuse it








Onto the outside now, i continued the stitching across the outer side crack's





Once that was done i melted across the join's and filled in any low's with the ABS filler rod's and melted them in.
You need to have the repair's slightly proud of the original level to allow for sanding it back flush
I levelled out the surface as much as i could, filling any pit's etc





Now you need to sand back the welded area to get it almost flush with the original, i use the 80 grit paper and hard block first.
Leave it slightly high so there is enough to sand back with the finer 180 paper.




Once this is done, use the 180 grit paper to get rid of the 80 grit paper mark's.
Make sure the edge's are all feathered well to lessen the chance of making the pain 'bite up' and leaving jagged edge's around your repair's

And if you find any low's still you'll need to refill them with the ABS rod and soldering iron, then resand it

This fairing is all ready to prime, then let dry, and ready to rub back and paint later
I use 3 coat's, 1st coat being light, the 2nd a bit heavier then a heavy 3rd, with 3M plastic Primer, (10min's-30min's between coat's, depending paint thickness and on temperature etc) then let it dry for at least an hour on a warm day before rubbing back.
Once you are sure the primer has dried out enough (use fingernail test, if it dent's then it's not dry enough) give it a light rub back with 320 grit Norton Wet and Dry on a soft sanding block and plenty of water before masking and painting with you base colour coat, then clear

 

Yeah i have used similar stuff but found it isnt as flexible as abs welding, it seem's to break clean off the abs and i did everything as described in the instructions
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