We have a 99 Sportsman 500 that the previous owner had the High Output kit installed on. The problem is that while it will run fine most of time, every so often it starts acting up and cutting out in the midrange. Sometimes it will run fine for 30-45 minutes or longer before acting up and other times it will act up after only 5 or 10 minutes. It only seems to do when the engine is warm. When it acts up it will stop accelerating past the midrange. It will just cough and hiccup until you let off the throttle. If you stay off the throttle for a few seconds and then gas it again it take off and run fine for a few seconds and then start cutting again. We switched out both the CDI and the coil with the ones in our other Sportsman and that didn't help out all. We even took it to the dealer and he replaced the speedometer that quit working and thought he had fixed since it never acted up on him after that. As soon as we got it home and took it for a good long ride it started doing it again. Not sure what else to try or what could be causing the problem. If anyone else has had this problem or has an idea please let me know. Any help would greatly appreciated.

 

This may be a dumb thought, but here it goes. I went riding one day after a good rain and hit a huge amount of water and mine would spit and sputter when i got to midrange throttle, my problem was i had water in my airbox and my stock air filter was soaked, causing it not to "breathe". you said yours had H.O. system on it, maybe, just maybe, it isn't able to breathe correctly from the upgrade?!?!?! this is just a thought, try getting a bigger filter or when it acts up, take off the filter to see if it will still spit and sputter with it off. JUST AN IDEA, hope it helps. PB500

 

Disconnect the reverse speed limeter and see if the problem goes away. Its a black wire going to a module under the front cover.

 

Hi all new to forum. I agree with checking the reverse speed lmiter. But if that does not do it to me it sounds like a fuel supply problem like a fuel filter so when your on it hard the supply can not meet the demand for fuel and when you lift it gives the carb. bowl a chance to fill and then runs good until drained agin. just a thought.
good luck
jeff

 

JEFF10049

That is one of the first things I thought of as well, seems like it is starving for fuel. Checked the fuel filter and it is fine, so unless it is the fuel pump. The dealer said he didn't think it could be a fuel pump. I tend to agree that since it isn't doing it all the time that it probably isn't a fuel supply problem. I think it has to be electrical and I am kinda liking Charlie's idea about the reverse limiter. I wonder if isn't somehow getting activated in forward sometimes as well as in reverse. Now that I think about it, the reverse light doesn't come on when you put it in reverse. I figured the bulb was just burned out and hadn't had time to check it, but I wonder now if it isn't all connected somehow. Thanks for the ideas guys. Hopefully one of them will solve the problem.

polarisbear500

It has a K&N filter that has never gotten wet, so I don't think that can be the problem. Thanks though.

 

ttt

 

Check the vent line from fuel tank to steering post,might have gotten kinked when reinstalling fuel tank after upgrades,also have seen too long a vent line going down into steering post (water sits inside of steering post and end of vent line gets submerged in water causing it not to vent.cut vent line so it only goes in post about 1.5"- 2.0" (not 6-9" as most new machines are)By the way,on a 99 500 the reverse limiter is run by the electronic speedometer,not the same as the older machines ,totally different wiring .