i have a complete yoshimura rs-2 exhaust and a k&n air fiter for my 03 400ex but i have no clue what jets to get! ive never done jetting before so i would prefer to get a kit. the problem is i dont know which kit, and which stage i should get. also alot of the jet kits are not coming with pilot jets. i am so lost and i really need help. please give me some advice on what jets to get and or what stage jet kit to get. i dont know if this is the right forum section to post this question but i am kind of panicking as there is limited information on the internet about this. links would be great. thanks for any help, i really need it!

 

Do not purchase a kit. Buy several OEM (most likely Keihin for your quad) jet sizes from Rocky Mountain ATV/MC or other ATV/MC site. If you contact Yoshimura and give them your setup, and location, they will be able to give you a ball park figure. Once they give you an idea, I would buy about 4 to 5 main jets in 2 sizes larger increments and maybe even 1 jet two sizes smaller even though the chances of you needing a leaner main jet from what they recommend are slim. It is usually not a 1 step process, which is why you need several jets. As you probably know, it is best to have it a little on the rich side.

 

oh ok awesome. i actually asked yoshi what i should get and they said to call dynojet and ask them what to get so im actually about to do that now. another person told me that they just get their jets from the honda dealership over the phone, do you recommend that??? also should i get pilot jets to?
what about ordering from this site, i could not find the right jets on rockymountain
https://www.jetsrus.com/a_jet_kit_at..._1999-2008.htm

 

Yes, that website would be fine, and yes, you could also get them from the Honda dealership, but I have found that RM ATV is typically cheaper. There are some parts that OEM parts are just better than aftermarket part. Jets are among these. Hopefully someone with a similar setup that lives in your area will chime in to let you know what they are running. If you get the info from Dynojet, then you can cross-reference their jet sizes to Keihin jet sizes. Remember to get multiple jets and do plug reads until you are dialed in. As far as pilot jets, it would not hurt to have a spare and a size leaner and richer. You usually don't need to mess with the pilot jet since it is responsible for idle and a hair above that.