Over the last few weeks, after the failure of attempting to use a soldering iron to mend the broken plastic on my VX, I decided to try my hand at using a plastic cement, or "chemical welding." As a complete novice, the pieces came out rather well.
Before getting into the details of this, the standard disclaimer applies: I am just a beginner; this may not work in all situations; this method my not be optimal but worked for me; I am not responsible for ruined plastic, fiberglass stuck in your skin or fingers stuck together. Remember... YMMV.
First things first. There are several different types of plastic used on motorcycles. Luckily most plastics are marked. In my case, it was not. However, there is a typical rule of thumb that unidentified black plastic is ABS (Acrylonitrile butadiene styrene). It is important to know what kind of plastic is being repaired. Mismatching plastic to cement can cause your plastic piece to liquefy or do other bad, bad things.
After some research it was determined my parts were indeed ABS. A quick trip to Lowes and less than $10 yielded enough fiberglass sheeting and ABS cement to fix two dozen motorcycle plastic pieces.
The type of cement used is Oatey Medium Black ABS Cement. It is intended to be used on ABS plumbing but works quite well in this application.
DO NOT smoke or have open flames nearby while doing this. The cement releases flammable chemicals while curing. JUST DON'T!
The fiberglass in the sheeting splinters easily. Use gloves while handling or expect to get fiberglass splinters. Further, USE A FACE MASK or OTHER BREATHING FILTER. Fiberglass splinters in your throat or lungs is NO FUN and can cause very bad things to happen. And, as always, when doing things like this, wear eye protection.
Step 1 - clean and scrub the cracks with warm soapy water (dish-soap worked well for me). Rinse well and allow to completely dry.
Step 2 - Cut a patch of fiberglass that will overlap the crack or break by at least 2/3 inch on either side. 2 inches overlap would be even better. Cut the fiberglass with a fresh razor blade, not scissors. Scissors will splinter the fiberglass badly.
Step 3 - Apply a liberal amount of ABS cement to the inner part of the plastic piece, where there is no finish or coating. If there is any finish or coating on the inner part of the plastic, it must be removed. This only works when the cement contacts raw ABS plastic. Be sure to get the cement into the crack.
Step 4 - Apply the fiberglass patch.
Step 5 - Apply enough cement to saturate the fiberglass and adhere it to the plastic.
And here is the finished product from the inside. It isn't pretty but after completely curing for more than 24 yours, this patch seems to be just as strong as the surrounding plastic.
Part 2 - coming soon. Complex Cracks and Ready for Clear Coat.