I just got a used White Brithers E-Series slip-on exhaust for my 400ex and most people have told me that I do not have to jet the fourwheeler. Do I or do I not have to jet it?

Thanks

 

I have the E -series full system on my Z400 and open airbox with powerfilter and it needed a rejet. Im not too sure with the slip-on but i would assume yes you will have to rejet. You should open your airbox and get a perf. filter first if not already done then rejet.