I have a 2004.5 sportsman 400... i see everyone talking about a K&N for improvements...
How much improvement do you get? What is the stock HP on my unit anyways? How expensive is a K&N and how hard is it to install?
Thanks again!

 

the k&n is simple to install take the old air filter out and drop that one in. it lets alot more air in and you wont notice alot of power differnce just a throttle respone. plus the k&n is an essential if you are going to do other mods such as a pipe. the k&n is awsome b/c once it gets dirty you just wash it witht eh cleaner put some of the oil on each pleat and it is as good as new you will never half to buy and air filter again as for the hp on your machine im not sure check your user manual it should tell you or maybe look on your engine my says 22hp on the sticker or the recoil.

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1999 250 trail blazer
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k&n filter DG exhaust for now
just to make it a lil lounder
titan 489 xts on the back
maxxis razors on the front
full skid plate,bash gaurd
rebuilt trans,D.I.D chain
pro amor belt,scott grips
the newer model tie rod ends
12 t front 36 t back sprokets
neon shifter ****, pro burner lights
stronger back caliper holder i made at a friends shop
cut front fenders with the floor boards removed
and makin some out of aluminum dimond plate

 

well urs is 4x4, then u will prolly want to get stock air flow, if u jsut plan to change the filter to a kandn, its very simple. If kept stock just go to www.rockymountainatv.com or dennis kirk or any place that sells filters, and just take off the air box lid. And put the new filter in there. Its usually comes pre oiled so no worries, but after riding in dust u will have to clean it, just look at the box u get with the filter. You will get increased horsepower by prolly 2 to 3 maybe. You might have to change the jetting. Im' not sure. Ask someone with a 400 sportsman who has done this. I put a clamp on filter to the carb (k and n) i moved the jetting from 170 to 180. I have a trailblazer thuo.

 

You shouldn't have to rehet with a K&N. The machines come a little rich from the factory. The main reason people are going to a K&N is for some improved flow, and the fact that they are washable and re-useable like BT250race mentioned. The last filet you will have to buy. Rocky MT ATV has about the best price around. I would also suggest getting an Outerwears or Prefilter (same thing) They really help to keep the filter cleaner for a longer period of time

 

ive been looking for a k@n filter for my 2004 1/2 sportsman......their web site doesnt list one.does anybody have one on their 2004 sportsman?where did you get it?

 

Go to Rocky MT ATV. They are $31.99 there. The ones that they list for the SP400 will fit as well. They didnt (at least to my knowledge) change anything with the airbox. In fact, a filter for a SP500 SHOULD (therioticly) fit

 

i know for cars they increase hp 5 - 10% depending on your horse power. but i think just adding a filter usually ups yoru hp 1-2 which isnt really anythying. but again this is for cars but i would think it would be the same for any engine powered vehicle. on my 87 GrandNational stock hp was 245(underrated) but i added a k&n 9in cone filter and new MAF pipe and if u go by the 5-10% i gained somewhere between 12-24 hp. which i didnt. like they all said it adds some but nothing really noticable.

 

I have a 2002 sportsman 400 and put a K&N filter on it just because if you buy two paper filters you have just paid the price of 1 K&N filter and the K&N is reusable and will last forever. As for power increase if there was any it was not very noticable. I still run the stock pre-filter.

 

The SP400 and SP500 use the same airfilter - $15 for the paper filter, $9 for preclean sleeve from Polaris. $32 for a K&N is roughly 2 paper filters, and if the K&N ever gets wet/oil soaked, you just clean it and dry it - wet/oil soaked paper filters are trashed. Long run you are money ahead for the K&N.

Your paper filter should already have the K&N type outerwear (thin fabric - not foam) - If you get the K&N, just slip this sleeve over it.

ps - the SP400 at Rocky Mountain ATV is for the 95-96 2 strokes