chayat, most side fairings are a nylon and abs mix except yamaha which is polypropylene. the rest of the fairings are abs. i work on sportbike bodywork everyday that how i know but yes you can plastic weld them back together no problem. the only issue with a soldering iron is the temp is completely uncontrolled and or way too high for plastic so 90% of the time the plastic is cooked from the heat and its half broken down, charred or boiled making bubbles which results in a weak weld. its really not much different than welding metal. for a strong weld its experience and having the right tools for the job.