Heating the plastic usually makes it brittle in my experience.
I have very successfully used some "Plastic Weld" 2-part epoxy, which I found readily available at Walmart, or almost any automotive store. The stuff I have in front of me right now is from Walmart made by ITW Performance Polymers in Riviera Beach, FL. It comes in a double-pump syringe type black tube. I have used this on the NSR and an R1 I owned (different plastic than the Honda stuff) and it worked perfect! It etches itself to almost any plastic, and dries to a semi-flexible state (almost identical in elasticity as the stock Honda plastic). I also tested it on a junk piece, and it adheres extremely well, flexing as if there is no repair present. I could not get it to break at the repair. I even used it on the Yamaha to "make" some small mount tabs that broke off and got lost.
With pieces broken completely apart, I tape / brace one side to line up the plastic. Then I V-cut the other side about halfway through the plastic thickness. Fill the first side and let it cure (about 20 minutes) and do the other side (V-cut/fill).
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Paul Herr
'88 FZR4/GSXR/YZF Frankenbike
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