My friend has a 2001 Sportsman 400. He would like some more power out of it and not loose the top end. I am thinking start with the K&N with a larger jet, raise the needle 1 clip, FIND a pipe for the 400, it seems like its a task. Not really sure what to tell him.. Can ya help me out?

 

We had a 425 Expedition, which has the same top end as your friend's SP400. We put a 500 H.O. cam in it and a bigger carb and manifold. I think we put a TM 38 flatslide Mikuni in it, but I forget exactly what it was. I also opened up the stock exhaust a little. The results were impressive, for not too much dough or trouble. The EXP has a speed limiter in it, because of the manual gearbox. I believe the SP does not have the same limiter. Point is, the EXP would not go any faster, just got there quicker. It was worth doing. I have an extra H.O. cam if you are interested...PM me.

 

Suppertrapp makes a good pipe for the 400 aka 425 and it will really make it turn on.

 

a H.O. cam and a bigger carb and intake manifold will help.

as will a high compression piston, or you can use a 500 jug and piston for about 455cc displacement.



but on the less involed side of things..
a K&N filter and jet kit will help, and you can take off the stock muffler and on the intake side of the muffler widen the slits on the inside with a screwdriver, not much gain buts is a free mod.

if you don't wanna spend the money for a jet kit, you could probably go one size larger on the main,but leave the clip position alone,and the pilot size should be fine too.


as for an exhuast, that should only be done after a bunch of other mods have been done first, since on a stock machine you will see very little gains for the money spent.

 

Personally I would do the pipe first along with high flow filter.Then jet the carb to the pipe and filter.Next would be clutch spring changes.The ones I am running in my 425 do real good.When I did mine I did the springs first then filter and pipe and jetting last.The pipe made the biggest improvement.

 

On your 400 sporstmen you can put a heelclicker clutch kit on it and Gain through the intire spectrom of perfomance.Top end gain around 8mph.Not losing but gainnig low end ,med and top end.For pulling its all horses .For mucking and trail riding its all tracktion and speed.Nothing but performace.I put one on my 400 ,,and its the best thing I ever did for my machine.The other clutch kits out their ,,you will lose some where in the spectrom of performace, just read the forms.

 

The displacement is 465 with the 500 jug.

 

For a exhaust its not worth the cost v/s the perfomance gain that will be nill. If you go with a heelclicker clutch kit the only thing you will gain is performance. You will not lose but gain in low,med,all the way through the spectrom of performance. Other kit manufactures offer 3 kits....and you decide where you want to lose in your performance range. heelclicker only offers one thing ,,,Performance through the entire spectrom. I don't know why people want to be second or third. When it comes to the leading clutch kit that Polaris's own racing team uses,,Its heelclicker #1 in the industrie today.I have had just about every kit that is offered out their and they all fall short of being frist.You want the edge ?heelclicker is #1 Proven Fact

 

Where do you guys get that a pipe doesnt give you that much more power?I have one of these bikes and that is the biggest improvment I have made.A motor has to breathe and the Polaris muffler is a plug.A high flow filter a pipe and rejet to the pipe thats the main thing.Then do your clutch there is times when you dont need a complete kit just a spring change like when you have a 4x4 and your not into speed just lowend.I can see doing the whole thing if you are into dunes or drags but on the trails all you need is low to mid range power.The way both of mine are set up work great for my type of riding and I dont have a mint in them.I know that there are alot of people out there like me that want or have to do things on a budget those are the ones that my advise will help.I know that some of you spare no cost but some of us cant. This is just my .02 worth so I hope no offense is taken.