I have on 05 Vinson that I bought new about 9 months ago. I have 500 miles on it with no problems until this weekend. The cooling fan ran about a third of the time I was riding. That's not normal since the outside temp was about 45 degrees. The rad was cleaned thoroughly after the last ride and the coolant level in the rad is full and the overflow bottle is fine as well. I'm wondering if anyone out there has had this problem. If it was a warm day I might have actually overheated but due to the cold temps it was fine.
Does the Vinson have a thermostat? If so could this be the problem? Also, this quad has no engine mods what so ever and has never been worked on.

 

I noticed this too on my new Eigers. Cooling fans ran 1/3 of the time we were out... even came on a few times coasting back down the hill (2-3 miles) using almost no throttle! Temp was about 40F

I'm gonna pull the plugs and see what they have to say. The dealership jetted them with a 115 jet for our 5,200ft altitude. We were up riding at around 6000-6500 ft.

Temp light never came on, so maybe this is normal for the oil/air cooled Eiger?

 

The vinson has a thermostat on for the switch on the fan. One for the temp light sensor and an ole fashioned one like on the truck you tow your bike w/. It's on the top left of the engine. Look at the radiator hose just above the shifter cable. It's in the housing w/ two bolts. Here are the steps to test it.
1) Pass a string just through the outer frame ring and make sure it won't interfere w/ the spring or thermostat function.
2) Put some water in a glass beaker (it atleast has to be something you can see through, you're only looking for 3mm of movement).
3) It should open between 164and170 degrees F

Of course dunno how much new ones are, for less than $20 I'd rather just change it than go through all that bs. One thing you may want to look at is even though you've cleaned your radiator it may not be truly clean. You also could have damaged fins or something that would keep it from cooling at it's maximum potential. I've actually had my fan running for almost an hour straight, but we were running slow and difficult stuff. What kind of riding were you doing? Go down to your local hardware store and get some refrigerator/Air Conditioner coil cleaner. Hit it once or twice and see if that helps.
If youre thermostat was stuck I'd figure you'd definitely be overheating, imho.
Good luck.

 

The fins are in perfect condition. I used to work for a radiator manufacturer so I'm well aware of how fin damage can cause problems. The fins per inch is too high thus it holds even the smallest pieces dirt and debris. I'mn going to remove the fan shroud and fan assembly to see if it is holding some dirt in there. The fan shroud is right up against the rad so maybe it's holding some dirt in there.

 

Yesterday I washed up the quad and sprayed the heck out of the rad. After I was satisfied I had gotten out all the dirt and stuff I decided to take the 4 bolts out of the fan shroud and move it away from the rad. To my surprise it was full of mud, sticks and small stones. After hitting it with more water and some compressed air I was finally able to get it fairly clean. I'm sure this is a build up of stuff since new. Those of you that have a Vinson you might want to do the same as I did and get that crap out of there before you overheat on the trail.

 

Well I'm glad to hear it wasn't a major mechanical issue. I myself questioned the plate directly against the radiator, but w/ the location of the radiator it'd be extremely vulnerable to rocks from the wheels. More so than sticks from the front imho. On another forum a guy referred to removing the rad every four rides for cleaning. Effective but quite tedious I imagine. Let us know if she's still hot under the collar on your next ride.

 

I had read of this problem on this forum in another thread. As a result, I've placed spacers between the fan and the radiator to allow more water to flow down. I just had my ATV mostly apart, but did not remove the fan for further inspection. I'll have to do that. I do make a point of spending extra time on the radiator with the pressure washer to try an blow out any dirt that may accumulate.

 

I also thought about shimming the shroud with washers but then I thought it might make the fan a little less affective with a gap there.

I was thinking about taking the rad out but figured I would make it a point to clean it better and see how it does.

I plan on doing some riding next weekend and hope all is well. I do hit a lot of the deep stuff so I'm sure that's the reason for so much junk being in there.

 

I've not had a problem with the radiator overheating since putting in the shims. They are only about 1/16 of an inch thick. Just enough to let the water run down freely. After each ride, I spend extra time with the pressure washer on the radiator to blow out any debris. So far, so good.