Don't use the Muzzy Fans!!!!
#1 : Engine will run hotter, the fan really doesn't live up to what they say it does. I'm in Arizona... believe me, the bike ran a LOT hotter in summer using Muzzy Fan over the stock fan.
#2: The blades BREAK. The metal is CHEAP. I had a fan blade (Muzzy) break off and hit the radiator coil. Luckily, it caused no major damage. However, when the fan came on the whole bike seemed to vibrate weird.
The stock fan is GREAT. If you are running too hot, check to see if you got that white gunk build up on the bottom of your coolant overflow. If you do, remove the plastic bottle, clean it out, and refill. The gunk that collects actually blocks one of the tubes at the bottom that goes into the radiator... this is what typically causes the overheating... the radiator can't suck in enough coolant.