I have an 04.5 Sportsman 500 that just started acting up the other day when I was plowing. It was running fine and all of a sudden it started missing badly and barely would run. It felt like it does when you don't have the reverse override button pushed and it starts cutting out. I made it back to the garage and performed the following:

Checked the plug, it was black and sooty.
Compression check was 75psi.
Checked the carb, drained the bowl and blew out the jet as well as checked the diaphram, nothing apparant there. Gave it some fresh gas and some Heat.
Checked the ETC and it was working OK.
Disconnected the electrical connection from the gauge pod to see if it was faulty, started the engine like the manual says and it still cuts out when you give it about 1/2 to 3/4 throttle, it won't rev past that point and just cuts out. I idles fine though.
I've run out of options and wondered about two things: Could I have burned a valve? Or could the stator have gone bad? Where do I go from here?

 

you could try a fresh plug. it is getting a strong spark?? that compression being so low, you may want to take off the valve cover and check the valve clearance(should be .006 for int.and exh.) that should give you another clue. check the cam lobes as well

 

I put in a fresh plug and checked the valve clearance, they were fine. Problem still exhists though. How can I check to see if the spark is strong other than seeing the plug spark while having it grounded when turning it over? Based on the valve clearance being OK I assume the cam lobes would be good too. How would I check the lobes anyway without taking it apart? My next move it to take the carb off and completely tear it down and clean it out but I'm not too confident that will fix it. I'm thinking that it's somehow spark/ignition related but where do I go?

 

Well I torn the carb down and replaced the float needle and seat as it has some slight wear on it not allowing the float to release consistantly when I would put the vacuum to it and tip it upside down. After firing it up it still wants to die when I hold the throttle halfway open or so. I took the air box cover off and it runs a whole lot better but still acts like it's wants to die unless I pump the throttle then it will rev up nicely but if you just hold it at a steady throttle position it wants to miss and sputter. Based on that it's telling me 1. it's not getting enough air for the amount of fuel it's getting but what could be the cause? When the problem started it was like someone flipped a switch so I'm wondering what went wrong.

 

I just took my fuel pump apart and this is what I found. This doesn't seem normal but how does so much dirt get inside it?

 

I finally have up and took it to the dealer and he even had trouble fixing it. He went through all the steps I did, fuel, spark, etc. and couldn't find the problem. Second time around he found the problem, it was a small ring under the main jet that had deteriorated over time causing an excessive amount of fuel to enter the main jet system. The machine runs great now. The dealer had about 6 1/2 hours of time into it and only charged me 3 hours, which made me happy. The part number is 3130919 if you want to look it up. Never even saw this part when I had the carb apart.