i have a 94 sportsman 400 2 stroke. i just added a temp gauge, had to drain water. at first i rode it and at 150* water level would rise all the way and start to spu out top. then i remembered about the screw on the head to let the air out. i poured water in radiator untill water came out the screw then tightend the screw. i filled coolent level bottel to min postion. then when it gets to 150* water level rises to maximum position. i then turn on my fan with my switch, and the water level dosent go any futher. i put in preston coolent., did not mix with water. i did not think the water level was suspose to rise at all, and at 150* did not think that would be hot enough to cause the water to leave radiator and go in bottle. just hope it is not a blown head gasket, are water pump, any help would be very helpfull

 

Is it possible that your rad cap is passing allowing coolant to leak into the overflow bottle?
Just a thought.

 

Are you saying you used prestone coolant and did not mix it 50/50 with water?
If so that is your problem .Antifreeze has zero cooling abilities you must mix it with water.
The reason you add antifreeze is to lubricate the cooling system.
water alone is bad because you dont have any lubrication.striat antifreeze or too heavy of a mixture will cause you engine to over heat.
the rad cap is supposed to leak the colant in to the over flow tank if it gets too hot thats why its called an over flow tank.
Try mixing your coolant 50/50 and use a proper antifreeze like Dex-cool ) also know as(havoleen extended life)

 

thanks i will try that today

 

I have a 99 Sport 400 with the same problem.I was at the dunes when I noticed coolant around the rad. What had happened was that it blew off the over-flow hose on the top of the rad. After that it was a catch 22. Fill up the rad, run for a few minutes till the overflow bottle would fill up and blow off the hose and lose coolant. It would then run hot due to lack of coolant. Can't win for losing. Brought to dealership. They claimed it was dirty/plugged rad. Got it back and ran it about a mile and it ran hot(light on). Brought it back again. This time they said it was low on coolant. They filled up and could not duplicate the problem. Of course they would only ride in parking lot and let it idle. Brought it home again and went for a easy ride with neighbours and when we got back the overflow bottle was filled to top and pressurized. I starting to think I have a blown gasket that is pressurizing the coolant system. Can't think of anything else that would cause this problem. It is still under extended warranty. Thinking I should just run it till it blows up and then they will figure it out. Hope this helps.
99 Sport 400 K&N filter.

 

It appears that you fellow are suffering from:

Inoperative fan switches

A fan which is not spinning on the fan motor shaft

or a clogged radiator

air in the system

or any combination of the above,

most likely the first suggestion.

Fix the automatic fan switch first and hose the black gumbo out of your radiators for about an hour.

Been there- "Lived through a 95 Sportsman 400"

 

Fan cycles on and off just fine. Also have replaced fan blade twice as the design is weak. Coolant looks like new(very clean) Have not totally drained and re-filled sysyem. Should get a chance to run it again this weekend. Weather here as warmed up to around 90, so it should be easy to get some fast results. Will keep you guys informed of what I find out.
99 Sport 400 K&N filter

 

What brand, size temp gauge did you use. Where did you locate the gauge. Just curious.
Thanks.

 

I finally convinced the Dealer that my quad has a major problem that is not going to go away till they take it apart to figure this thing out. They found blown head gasket and warped head. Will be getting new head and top end. Parts on order.
99 Sport K&N Filter