I just ordered the white brothers ecr exhaust and a K&N air filter for my 04 Z400 the exhaust said it includes the jetting needed, is this correct? Also how much of a difference will this stuff make over the stock. What should I do next to make my 400 have a little more power I use it as an all around atv (trails, tracks, slow riding, and all out in fields

 

most pipes come with some jets, you will have to mess with the jetting till you get it right or have somebody do it for you, as for power you will notice it, for more power think about cams, a cdi box, pro flow intake and a good air filter. the list can go on and on for what you can do for power, and welcome to the forums

 

I wouldn't mess with those jets they send you. Go to your dealer and get Genuine OEM jets. You should start with a 160 main and bump up the pilot to a 25. This is without the air box lid on. I use a outwears lid cover which lets it breath but keeps a lot of dirt and dust off the filter. If you want more power you got to op[en both ends up. More air in + more Gas + more air out= more power!