Depends on your dealer as to whether they claim Polaris knows about it or not. STock should be 167.5, Mine was, drop it to a 165 and try that. Only Takes a little bit of time, alotless than loading up the quad hauling it to the dealer, then possibly waiting 3 days until they can get to it..If you havent Jetted a Carb before its nothing to labor intensive, and I or someone else here can walk you throught it, I got to the point when I was doing jetting runs that I could Have my Carb, off and Jetting changed 9 times within an hour.

Honestly Though, I recommend a Dynojet Kit.. It Really Helps these machines.

Ron
04 Sportsman 400
K & N
Dynojet
HeelClicker

 

Both of mine came with 172.5's and so did 2 guys I ride with. I bought the Dynojet kits for mine, they ended up with 165's in theirs. I think the Dynojet gives more power. I can wheelie in low with alittle body english, they couldn't. It was hard to compare apples to apples because mine have EBS and theirs don't, (I read somewhere EBS takes more HP to operate than without and thats why Polaris does not put them on the 400's from the factory). Probably BS but sounded reasonable to me. As far as long term comparison between Dynojet and factory, they both traded for 500's so can't help there.