I use the ACS Crossfire Freewheel on my builds as it accepts either multi-speed or single speed chain. In this way, it does not matter if my [Crank] or Front Sprocket is single speed or multi speed, it will accept whatever chain you are running. I like to avoid using the chain pulley tensioner from motorized bicycle kits on the motor drive side if at all possible. If you want to equal the chains out so they are even (without a chain tensioner) you may be able to accomplish this by adding or reducing teeth on your bicycle crank side freewheel.
DOES NOT REMOVE STINGRAY FREEWHEEL - THERE IS NO TOOL FOR REMOVING STINGRAY FREEWHEEL. This is a special removal tool for removing the ACS Crossfire FREEWHEEL that we recommend on this site. NO OTHER FREEWHEEL TOOL WILL WORK ON THIS style Freewheel. I only use the ACS Crossfire Freewheel on my builds as it accepts either multi-speed or single speed chain.