First of all, this is not my atv, it is my friends. He has a 2000 Polaris Magnum 325, and it seems to hve a problem with overheating after extended high speed use. It is brand-new, and un-modified, and has been well maintained. After high speed riding (such as on the road) it will start to pop, backfire, and lose power. The only thing I can think of is maybe a jetting problem (too lean), or mybe it needs a colder plug. What does everyone think of this problem, and has it happened to anyone else?

 

Mine did that and it was from that little vent hose was kinked and after that i doesnt do it any more

 

Pull and check the spark plug cos there is a lot of information there. Once you have it removed check the colour, if it's white it is too lean. If this is the case it will run hot and can cause the problems you are experiencing.
My 2 bits for the day.

 

Do a search for overheating problems. There have been many discussions lately.

There are some problems with the new machines with bad sensors that control the fan and also rads that are missing a baffle or something. Both are warranty issues.

One other common cause is mud in the rad restricting air flow and cooling capacity. Many have reported that the rad looks clean but a good flush reveals caked in mud.

Good luck,

DJ

 

I have a Magnum 325 2x4, and it will pop, but not with wide open throttle - it happens when I've been riding at higher speeds, and then come to a descent that I use the engine to brake, and then it will pop the exhaust when I give it some gas (specially if I press it suddenly). I think the mixture is too rich, and some gas is being left unburned in the exhaust system, and then exploding inside it. This also happens when for some reason the engine is turned off and I don't notice it immediatelly (like the key chain getting stuck on the gas filler cap), and keep the throttle on. When I start it again it will also pop.

Any comments from the experts? This is just a theory.

Pedro Pinheiro