As a teenager my second ever job was as plastic welder, I'd take my total busted-up rear mudguards of my RM125 and weld them all back together. The tool I used then was just a heat-gun with funnel on the air outlet but with a feed-hole to feed in plastic filler rod. We use to weld PVC and polypropylene (what dirtbike plastic bits are made of).
Now I just used a soldering-iron with either plastic cable ties or plastic parts cut into strips, hardest part is keeping all parts molten.
Not long ago I made a oil-catch belly pan for one of my roadrace bikes, welded it all together with my $10 soldering iron.
