Hi Guys,

I have an issue on our SP400 that may be jet related. it seems to sputter when going up a good hill at full throttle. A few weeks ago we went to iron County WI. and my bro-in-law rode the SP400 atv. It seemed to sputter more up hill with him on it since he is about 40lbs heavier than me. if you let up on the throttle it will stop and creep its way up the hill. The bike has about 1900 miles and 100+ hours on it. I have done the valve job with only minor adjustment about 1.5 yrs ago, replaced air filter & cleaned the pre-filter before the ride. In an effort to troubleshoot we took the airbox lid off and ran 1/2 a day like that and it ran great! No sputtering or anything. (kind-a loud though) Would the airbox on these be restricting the air that much or is it a jetting issue where it is getting too much fuel. outside of that it runs great! Thanks for your help!!!

 

Have had some customers just pull the air box lid if they go up in altitude to help lean it out especially if its not too high up to where its not worth rejetting. Down here in Texas at 600 feet,pull the lid and wont hardly run!

 

My 05 Sportsman was doing the same thing. Turns out the breather tube was sucking on the gas tank at high throttle. Adjusted position of the foam spacer on the breather tube and problem solved. Runs great since.