I have a 1998 sportsman 500. I recently had an issue with with a leaky radiator. After fixing that i filled the tank with 93 octain, and put on a new K&N filter on it. Now when I hold it WOT it sputters and back fires and has no power at all. I took the new filter off and put the old one back on to see if it made any difference, which it didnt. I went up the street WOT and it gets up to about 35 and sputters, if u let off and get back on it i could get it to do a little over 40, but you have to constantly let off and get back on it. I am thinking possibly a spark plug issue? I canged my oil with the correct polaris oil and filter, and only have about 2 ride hours since the oil change. Now the quad has been sitting for 2-3 weeks, but its never run like this before.

Any thoughts???

 

You most likely answered your own question, try a new spark plug and get back to us.

 

try unplugging the black wire from the rev limiter box. it gets said all the time but it can go out spontaneously and cause weird problems

 

i'm new to these machines, where exactly is the rev limiter box?

 

<div class="FTQUOTE"><begin quote>Originally posted by: blackbronco

i'm new to these machines, where exactly is the rev limiter box?</end quote></div>



its number 32 on there

 

Thanks for the diagram! Tried unhooking the rev box, no difference. Got a new plug, runs a little better but still breaking up bad at high RPM. A good carb cleaning is next on the list unless someone has another opnion?

 

check for loose connections between the spark plug wire/coil and plug wire/boot. sometimes they wiggle loose. could be at high RPM the vibration is causing a loose of continuity.

 

<div class="FTQUOTE"><begin quote>Originally posted by: blackbronco

I have a 1998 sportsman 500. I recently had an issue with with a leaky radiator. After fixing that i filled the tank with 93 octain, and put on a new K&N filter on it. Now when I hold it WOT it sputters and back fires and has no power at all. I took the new filter off and put the old one back on to see if it made any difference, which it didnt. I went up the street WOT and it gets up to about 35 and sputters, if u let off and get back on it i could get it to do a little over 40, but you have to constantly let off and get back on it. I am thinking possibly a spark plug issue? I canged my oil with the correct polaris oil and filter, and only have about 2 ride hours since the oil change. Now the quad has been sitting for 2-3 weeks, but its never run like this before.



Any thoughts???</end quote></div>

[img]i/expressions/face-icon-small-happy.gif[/img] If haven't addressed carb,just might be water or trash at bottom of bowl causing backfiring and running bad! Dont know if this is your problem,but have had several that have had same symptoms when accelerating. Just a thought?

 

carb is clean and wasnt to dirty. It almost feels like my muffler is clogged. I tried to get the bolt out of the bottom with no luck. I will try running it with no muffler to see if thats my problem... I know this will lean it out, but it will be a very short test run up the driveway.

 

I have a very similar problems. Good luck with this one.. I have been stuck trying to fix it for over a year. Sounds like the bad cam symptoms.