I have a 1998 sportsman 500 with quite a nagging problem. It idles fine but when you try to give it throttle it starts sputtering and spits gas back out of the carb. I thought maybe the pilot screw wasn't adjusted right so I checked the spec in the manual and reset it. No change though. i have even pulled the carb off of a fullly functional identical model and there was no change. this led me to search for an electrical problem. I have checked everything from the stator to the etc mechanism and everything checks out fine. I am stumped and need new ideas. I have heard of several other 500's with this identical problem so I am hoping someone out there has conquered this thing. Please let me know something. Thanks, ****

 

Sounds like the electronic throttle control has gone out on you. For some reason that doesn't sound like the right name but thats going to be the area the problem will be in.

 

did you change the rubber manifolds, or just the carb? could be a cracked in the one between the carb. and head...

 

Mine did that too. I had to hold the override button in to go faster in forward gear. After a couple minutes it would return to normal and I didn't have to hold it anymore. That only happened in the extreme cold (below zero).

 

Many times, a backfiring through the carb is an indication of a lean mixture. Two causes are lean carb problems, or even valves that are adjusted too tight. Just a thought.

 

Where is the electronic throttle located? I am aware of the shutoff switch just above the thumb throttle lever (close to shut down the engine).

I have a 2004.5 that will allow me to slowly bring the RPM up to 3800-4100, but will stall if under any load - forward or reverse. It stutters just like when you are in reverse without the reverse button pressed.

Any ideas?

 

Try adjusting the throttle cable, there should be very little slack, the adjustment is three or four inches away from the thumb throttle.

 

Thanks for the suggestion. I checked that shutdown switch adjustment, and it is fine. Do you know where the reverse overide output is (where it actually causes the engine to stutter/stall)? Is is possible the switch is defective and causing the engine to stall in in forward? Of course, I've tried pushing the overide button, but my engine stil stalls under load.

 

you might want to check the engine timing as well.....

 

Try to just let the quad idle and then turn on your lights!!
This will put the ECM box under a load and if it stalls ..That may be yor trouble!!!
It was mine..........Caper...........