Okay I searched a few posts and found no concrete answer so I'll try again. We have a 2010 400HO that almost immediatly after purchasing new a year ago we installed the winch and 25" tires and have never had an issue, mud, hot weather, snow, plowing, it always ran great. All of the sudden it is constantly running hot to the point the temp light is always coming on. they only recent change was we changed the front tires from 25x8 to 25x10. the fan is working, thermostat is good, waterpump is not leaking, coolant is full and flowing, radiator is good and clean (both sides).
My question is, with the winch(factory Polaris) sitting in front of the radiator and the wider tires, is this causing the machine to work harder and getting too hot? The quad just turned 30hours. I'm tempted to put the 8's back on front, but before I do I was just hoping someone out there would have a little advice or knowledge for us. thanks

 

Welcome to the forum! Could be lack of air flow to the radiator,have had a couple on the forum with this problem. the hot light would kick on even with the fan operating.I'd make sure the back of the radiator is clean,I've found some caked with mud and have even removed the fan to clean thoroughly. Also remove the radiator cap and run until the fan cycles on, just in case you may have a little trapped air (can cause overheating) then top off radiator and coolant bottle. With only 30 hrs doesn't sound like the radiator or engine thermal switches could be the problem? Some times have seen a little "lag" on fan kicking on versus the hot light,but could be due as you say to air flow restriction. OPT

 

well I'm pretty confident the radiator is clean, but tomorrow night I will pull the fan off and clean behind that as well. and I'll pull off the rad. cap and let her run for awhile as well to see if there is an "air pocket" I'll keep you posted

 

The one HO I have had a dealing with was, the engine was running lean, and the addition of the extra work and lack of airflow was enough to send it over the edge. The fix on this bike was a jet kit. Never another problem. Look at spark plug, it will tell you

 

I haven't had time to work on it tonite, but I did pull the plug and it looks normal, and it seems to run fine, if it was running lean wouldn't the plug be white, and wouldn't the quad be hard to start? Being there are no performance mods on the bike could I get away with a carb adjustment versus a rejet? Just seems if the winch was blocking airflow the overheating problem would of been almost instant after the install. I'm going on a year with it installed.

 

Just an update, I checked the sparkplug and it looks good and normal, air filter and prefilter are clean. I removed the fan and the radiator was dirty behind it but not terrible but I did clean it out. then I removed the radiator cap and the coolant was full about 1/4"-3/8" below the very top of the neck. I started the quad and let it run untill the fan cycled a few times. at first the coolant rose to the very very top of the neck, then as the fan kicked on it dropped about 3/8"-1/2", then rose back to the intial height. I didn't see any air pockets bubble out so I reinstalled the cap. Does all this sound normal??

 

Sounds normal for the coolant to rise and drop down when the fan first cycles on,if any air was in the system this usually expels it. If the hot light comes on again while riding,could be air flow blockage as you mentioned or you can't rule out either of the sensors being faulty even though you only have thirty hours on the atv. OPT