I want to put a 17" front wheel from a 1989-91 750 or 1989-90 1100 on my 1988 1100. Will my 88 rotors fit the 17" wheel?

no, i believe the bolt patterns are different. you'll need to use the rotors that go with that wheel.

the easiest way, though, is just to put the entire front end (wheels, brakes, forks, triple clamps) off an 89-91 750 on your bike. the steering stem goes right into the frame.

If you have access to a suitable lathe you can machine the inside dia to fit the 17 wheel and then redrill the bolt pattern between the existing set of holes so the rotor will now bolt on 17 or 18

Here's the page with the low-down on what you'll need to do. It helped me with my 7/11.
http://www.tidepool.com/~tetrault/trivialtech.htm

Good luck

If you want to sell your '88 front wheel, please let me know.