i have a stock 400 and want to gain low and midrange some top, i want to take off and sling some mud on my non-polaris buddies-
thanks for ur info

 

For lowend grunt set it up like I have my 400Sportsman.Start off with a Aaen Torquer pipe and silencer,hi flow air filter of your choice,Boysen Power reeds,rejet to these mods.When it is time for a topend port the cylinder and go beat the big boys.

 

trail porting is good and you should try to find a stroker crank for it