I am posting this for my father, he is trying to get a bit more power and torque out of his 2001 Sportsman 400. He was gonna upograde to something bigger, but for the amount he uses it just wants to put a few $$ into getting a bit more power/torque. He has the K&N in his wheeler now. What other options does he have? clutch kit, pipe, clutch spring etc etc. If you could please give me some good ideas, along with any good clutch kits(worth buying). For a pipe it must be quiet.

Also he is looking for a good set of tires, a good mud tire, tah twill still be good for everyday trail riding, rocks, dirt, hardpack, soft..basically everything. Also how big of tire w/o killing too much of the power.
Sorry for all the questions.
Thanks A Lot

 

Anyone?