For air cooled engines, this is a nice addition to help cooling. I wired up a computer fan with a toggle switch to help cool my Tao Rhino. They're all 12 volts. This one blows at 200cfm and was 20$ on Amazon.

12V computer fan.

 

Yes....I added one to my Praire 300 many years back, it was air cooled but also had an oil cooler. Mounted a waterproof 12v fan to blow back thru oil cooler and over cylinder fins. Worked great in hot summer heat, made a real difference.