I just picked up a tank 50cc for a friend. Needed some cracked plastic fixed. First I tried melting some zip ties in to the back of a crack. Just fair results. Then I got on the internet and found this page.
reading I also found mention that the plastic will melt with acetone, and ABS glue as used in plumbing which contains acetone. I tested the scooter plastic and found it did indeed melt with acetone. Then I found an old computer front had the same type of plastic that melted with acetone. I proceeded to cut it up with a band saw, and melt it in the back side and also made new mounting brackets out of it. I used a real big old electric sheetmetal soldering iron, the small ones used for electronics repair just do not have enough heat. (tip is about 3/4" in dia.) I will be sanding it all down tomorrow, so far it is much stronger than it ever was. Using acetone and plastic saw dust melted together makes a paste similar to a bondo filler to get the last little bit of imperfections and surface cracks. after sanding I will get a rattle can of Krylon plastic paint.
No pictures so far as I am not going to take a camera around acetone fumes and plastic fumes, they are nasty. john