Sorry fellas if this subject has been tackled before. I am new to this site and joined for this reason. I recently added an e-series s- bend silencer and a K&N filter with outerwear. I recently vented the air box cover with about 12 of those 1in. pop in faom vents. I started it up and it sounds kinda rough. I'm assuming I have to rejet it and have a kit. My question is this. I believe the stock main is a 155. The whitebrothers co. recomends 2 to 4 up. My kit goes up to 170 by fives. Does this mean 157-159, or 2-4 sizes by fives? Which would mean 165-175. Also just by glancing at some of the messages it appears many of you have this set-up. With a stock engine (no upgrades, ports,pistons, etc.) what did you run. Thanks for the help, I am new to four wheelers and four strokes!

 

i just went through this with mine..........

the stock jet is a 148........

i put the pro curcuit pipe on it and put a 152 main jet in it,
and it ran a little lean.................
so i put a 155 in and it runs great..................

( i haven't got a filter yet)

if you have the pipe and filter i would say try a 155 or mabe a 158,
i would try the 158 and go from there.........you shouldn't need much bigger than that.....

hope this helps a little.........

 

One thing you need to differentiate, when talking jettting, are they talking about stock jets or Dyno jet kits. They are not the same size jets. A stock 155 jet is not = to your jet kit 155 jet. Your jet kit comes with instructions. Use them. In your case I would start with the 165 jet in your kit. Then I would try the 170 jet and see witch is better. But you also have to make sure you have the needle and pilot jet set according to the directions in the jet kit. Your jet kit doesn't provide a pilot jet because they tell you to make this adjustment using the pilot screw. Does this all sound familiar from your directions? Did you adjust your pilot screw?

 

White bro means 2 to 4 available sizes. Keihin jets jump from 148 to 150 to 152 to 155 and so on. In other words they don't make a size 151 jet. Darius has good point too, some jet kits use mikuni jets for ALL their testing (well aftermarket mikuni jets anyway), and they are sized a little differently than keihins. So some kits I've seen come with numbers that are way different than the stock keihin number, although the claim is they flow the same amount of fuel as the keihin of a different number. Confusing? I sure thought so.

 

Hey thank you for the response. Yes, it sounds familiar. My jet kit is a dynojet kit and it came with that K&N power kit. I also did some research and found an article on exriders.com. It was exactly what I was looking for. the guy had the same setup with the same outcome. He said he put a 158 main and 42 pilot in. BUT, like you said my kit comes in multiples of five. I appreciate the info. big time! See I use to ride a 02 YZ 250. Miss the two stroke and two wheels!