Well, since you had 28 looks and no replies I will give it a shot. Not knowing what year your 750 is I would not know about the plastic pieces, but yes those carb cleaners love to eat plastic stuff. I used Gunk carb cleaner that came in a 1 gallon paint can with draining dip basket. It worked very well for me. A lot of the guys here swear by Simple Green. I would suggest removing the plastic, clean and rebuilt them totally. If they spent a lot of time in the weather like you mentioned, give them the total treatment. As far as where to find more info, try the FAQ area and do a search on carb cleaning. I think there may be a ton of stuff there. Good luck with your project.