In addition to BimmerFan's post. You can adjust the lower rotor belt tension as well. This will affect acceleration speed from slow (or stop) and will sometimes affect the actual fast rotation speed too. Some other things you can do; disconnect the fast motor plug for the lower rotor. I think it has a nice sound to it. Unplug the slow motor for the lower rotor. The rotor will coast to a stop rather than brake to slow speed. Lastly you can unplug both slow motors (alot of jazz players do this, including Jimmy Smith back in the day).