It's not the first time I've turned to the California Scientific (CalSci) website for moto information that's not just about windscreens. Mark's site is a fountainhead of helpful information, including the following: (and by the way, if it's good for the plastic windscreens, it's good for the other plastic too.)
Cleaning your Windshield We make our own cleaning fluid. When you buy a windshield from us, we give you a small spray bottle of cleaning fluid and a micro-fiber cleaning towel. Here's our "secret" washing fluid recipe, the result of testing about 25 different formulas:
Makes 1 quart = 1 liter windshield washing fluid
- 1/2 cup = 100ml ammonia (double this if you have a lot of bugs)
- 2 cups = 400ml isopropyl (rubbing) alcohol
- 1.5 tsp = 8ml car wash detergent (don't substitute dish soap or laundry detergent) (note: emphasis added)
- 2 cups = 500ml water
We recommend using only micro-fiber cleaning towels on your windshield.
If you don't want to play home chemist, go to WalMart and buy a gallon of Peak Windshield Cleaner (blue), about $1, and a gallon of Peak Bug Remover / RainX (green), about $1.50. Mix them 50-50 and use that on your motorcycle and in your car.