I will have a WB R4 silancer soon and I need to know if I need new jets or not. My dealer said I don't need it with just the silencer but if I get a new filter kit and cut holes in the lid I will need to rejet it. I don't want to buy the power up kit b/c you only need one jet and I will have the filter kit on it soon. My altitude is 1135 ft. Dose anyone know what jet I might need?

 

I have a supertrapp exhaust and a k&n filter I had never had to jet mine. I just added a wiseco 10.5:1 piston a racing cam and ported and polished my head. I just jetted it slightly.
If you drill holes in your air box you will need to jet it. But with a silencer and a k&n filter you wont.

 

to realize the maximum performance of you new pipe, i would suggest a prodesign intake system, with a foam filter not a k&n, k&ns wont trap as much dirt as a hi-flowing foam filter such as uni's, thats why all pro mx teams are using foam.
trying upping your main jett 2 sizes when you get your pipe, if it runs strong all the way to the top you're good to go, if the engine sputters on the bottom end with just a little throttle applied up your needle clip, a notch, this should cure that problem, keep doing that until its crisp all the way to top rpm! if you run out of clip positions up the pilot jet 1 size, then start at the bottom and work up until its running to your satisfaction. It's a little work but look on the bright side once its done right, since its a fourstroke you shouldnt have to touch it again, unless you modify it further.

Andrew Humphrey
99' wolverine procircuit pipe, prodesign filter system.