I have a polaris sportsman 600 twin. It seams like when its colder it will run longer and when its warmer it acts up sooner. After a few minutes of driving the atv it will lose power and backfire when you press the gas. If you just barley give it gas it will go but still won't take gas normally. If you let it idol for a min or so it is fine but will do it all over again if you ride it too long(30 min or so) or give it a lot of throttle for a short time. It does it again as well. I changed the plugs, drained the float to make sure there was no water and added dry gas. I checked the fuel filter and was like new. I even took off the gas cap going down the trail to see if it was vapor lock, nope. My dealer told me it was the Etc so he told me in the throttle cable adjustment I had to have no slack in the cable, I adjusted the cable so there is no slack at all and there was no difference. I am on my own here I think that it is in the ignition system but not sure. Does anyone have the specs to test the stator and coil? Any help would be gratley appreciated, thanks

 

Sounds like the pilot jet is plugged in the carb, take the carb out and take the bowl off and clean all the jets thoroughly with carb cleaner.

 

I would take the carb off and completely clean it. Also check the rubber boot between the carb and head they are notorious for cracking.

 

Thanks for your input, I did think of cleaning the carb but I do not think thats the problem. It idols great and has full power when cold, Soon as it starts to get warm(normal operating temp) it will do this. After I stop let it idol for a min, give very little throttle drive it like that for a few secs it back to normal. I can floor it and give it normal throttle and drive it like normal. Sometimes I swear it even has more power after this happens. Then after a little while of riding, blam! Same thing all over again. Sometimes I wonder if I am going to make it back home. I don't dare go to far with it because of this. I bought this atv from a local dealer this spring when it was still cold and he claimed he went through and checked the entire machine and it was in top condition. When I tried it out before I bought it I drove it in the snow floored it spun it around for about 1/2 hour and it never did this then. When he dropped it off it was out of gas but I put gas in it and it still ran fine, The only other thing I noticed was the plastic nut holding the key swicth was loose and moving around when I tried to start it, So I tightened the plastic nut firmly so it would not spin when you turn the key to start it. But When you turn the key all the way to start it now you have to manually turn the key back because most times it won't spring back to on or it will sometimes stick there and keep the starter engaged. Could there be something with the key swicth causeing the problems? Have to rest my fingers now I am all typed out!!

 

Had this same thing happening on my 04 700. There was a crack in the rubber manifold (connecting the carb to the head) It ran along the bottom of the manifold and was almost impossible to see. When the engine would get warm it would expand and the crack would open, sucking air, cutting out, and would die. When cold ran fine. Replaced the manifold cured the problem.

Trooper

 

I will check the manifold for cracks as soon as it stops raining and let you guys know what I find. I sure do hope I find out what the problem is,

 

How do I even get to the Intake manifold to tell, its so tight in there I can Hardly see it. Is the small yellowish line that comes up from in back of the gas tank and goes into the headlight pod the gas tank vent line? If so is it normal for some gas to be moving in there. And I am def going to need a new key switch its getting harder to turn now too.

 

I could drive it anywhere today as long as I only pushed the thumb throttle quarter or less anymore then that and in a few secs pops and cut out, go back to qaurter or less and it was ok. It never completly died to have to restart it. If it ever stops raining I will figure out how to get to that intake boot and take it off and check it for cracks.

 

Pull both side panels and the seat. You should be able to see the carb and some of the manifold. THe cab is pretty easy to remove then you can get the manifold out. Actually easier than changing the plugs The gas in the breather line going into the speedo pod is normal if the tank is full or gas is sloshing around, some will get into the tube.

 

One more thing: They usually crack on the bottom of the manifold. A quick test is to take a small piece of duct tape and stick it securely to the botom of the manifold. If it runs better there is a crack.