So you made a rookie mistake, but probably were spared damaging the engine. It's not guaranteed that you will bend a valve without releasing the tension, it's that you might.
There should be no danger in spinning the motor a few cycles to verify proper movement while rebuilding. If you're concerned, spray a bit of oil into the cylinder thru the spark plug hole. These are dry sump motors to begin with, so residue from previous running is all that coats the motor during start up. The combination of "dry" and "heat" is what does the greatest damage to the engine.
Just be certain you oriented the cam properly and your timing is set. Then button up and ride!