I was wondering what is the difference between just changing my jet and using a dynojet kit? I recently bought a pro-circuit t-4 full system for my 03 scrambler 500 and they told me not to rejet. They want me to install it then see what i need. The dealer says to bump up to a .160 main that that procircuit is full of it. Should i buy just a jet, or the dyno jet kit. And if so how much more work am i looking at installing the dyno jet kit compared to just changing the jet. This is new to me so im sure its gonna be fun.




Nez

 

I have the dynojet kit, I wonder the same thing as you, I want to buy a pipe but how does the jet kit fit in? I have installed jet kits before and this one doesnt seem to difficult however depending on the pipe is where things get sticky and thats what drives me nuts

 

I believe that with a Dynojet kit, you get new needles and shims. Dynojets are also sized defferently than stock carb jets, so if you hear someone talking about a (for instance) 160 main jet (stocker), that will end up being like a 128 Dynojet. I think Dynojet sizes their jets by the amount of fuel flowed, whereas other jets are sized (labeled) by the actual circumference of the jet hole. (I think that's right)

I was never a big believer in jet "kits". Just go buy a couple different sized jets from the maker of your carb, and try them until you get the right one.

 

When you are buying a Dynojet kit, not only are you getting an assortment of main jet sizes, but you also are getting a specially tapered jet needle (for better throttle response) and their experience and technical support of what combinations need what sized jets - theoretically they have already done all the "trial and error" in trying the different jet / needle combinations, and all you have to do is install.

 

I agree with your dealer, bump it up to a 160 main and adjust your air/fuel screw so that it is 2 1/2 turns out from lightly seated. Then you may have to do a plug check and see where that got you. When you put a full exhaust on like that, you are going to have to rejet.