I have the K&T black box on my Commander and the engine temp runs at 2 bars the majority of the time. On the same trail at the same time my Maverick is running 3 or 4 bars and even sometimes 5. It always worries me that the Mav is running so much hotter than my Commander. So I have the fan switch on order and plan to use it extensively this summer.
My thought is the fan doesn't even come on until it hits 5 bars which is 210 or so. My guess is the engine is designed to run at this temp without any issues. I doubt having it running cooler will have any negative affects so it comes down to personal preference and riding conditions
I live in middle tennessee and this weekend it was around 7o degrees . I noticed that the bars on temp would stay around half way while riding. With that being said , riding was with my wife and 4 yr old son in her lap so we really was more or less easing around with him in the mav. At times u can really fill the heat and i can smell it when running hot. I plan on wrapping the exhaust and using hushmat or something like it to help with heat. But more or less trying to see if the fan switch was a must have goody.