Rejetting

[Sawicky]

I have a 2003-400EX with a WB-E-series slip-on pipe. I still have the stock jetting in the carb. Does anyone know what size jets I need to get? Or do I just stay with stock or adjust the air/fuel screws...I feel a difference in the pipe when it comes to power and torque. But, I wanna know if I can get alot more out of it. Please give me some clues...:macho :macho

[JOEX]

You may want to go up a size or two. Everyone says the 400 is delivered lean and adding a pipe may lean it out more.
My suggestion from the info I got from here is:
40 pilot (leave the air screw alone)
150 or 152 main
Raise the needle one notch (this is disputed)

Joe

[trailburner]

the only thing you should have to do is go up on the main,there's no way i would leave it stock[too lean]. If the only thing you did was put the pipe on, you should be safe with going 2 sizes up on the main and do a plug check.

[Sawicky]

I put a 42pilot and 152main and 3rd gear is really lagging. feels like its way to rich. So then I put the stock pilot back in(38pilot) and put the clip back on the 3rd notch and 158main in...still is lagging. So I put all stock jets back in and it still is lagging. I'm gonna try to adjust the air screw...Please help...

[KY Woods Rider]

You didn't say whether or not you're running the airbox lid, but I'm going to assume that you are.

I can tell you what I'm running for my TC slip-on exhaust, UNI filter, and airbox lid on; it might not be perfect, but it should get you in the neighborhood. Also, my jetting is for 500-700ft above sea level; so if you are at a high altitude, you might be able to go a bit leaner.

I'm running the stock pilot, air screw 2 turns out, needle raised (clip lowered) one position, 152 main.

As JOEX said, the raised needle is something that some people like, while others prefer it in the stock position. My quad runs just a bit rich on the needle when the temp is over 75 degrees, but it is barely even noticeable. I can only tell it's rich right as it comes onto the needle (about 1/4 throttle) when coming out of a slow, tight corner. After an average ride, a plug check says the jetting is just fine. So for the needle clip position, if you ride only in warm temps during the summer, then the stock position should be just fine. Since I ride my quad in the winter months too, I prefer the raised needle and just put up with a tiny bit of richness during the dog days of summer.

[coryatver]

I have a 400ex with a t-4 slip on and stock air box lid/ filter. i rode it with a 148 and it ran fine and i put in a 155 main. i rode it for a little bit and pulled out the plug and it was grey and it ran ok and now i have a 158 main and it runs the same. how can you tell if it is rich?

[Sawicky]

You have to understand....If it isn't responding quick well then you might be rich because the fuel isn't burning fast enough in the engine. The carb is giving the engine to much fuel than it can burn....I think thats whats wrong with mine. In 3rd gear just cruising about 10-15m.p.h. and when you hammer the gas it hesitates...It feels like a 2stroke with power band. It shouldn't do that at all....I have all my stock jets and settings and it still feels funny. I'm taking it to a Honda Shop soon. I'll let you all know the outcome...Later..Tim:macho

[Tmac23]

hey guys i'm pretty interested in this thread because i have a white brothers e series slip on on the way. My quad is a 02 400ex stock i'd like to know what setup works the best with this slip on. If you could let me know what works I would appreciate it thanks alot

[Sawicky]

I don't know what else to do. I tried to adjust the air screw , this carb is really screwed up. I don't know what else to do. I'm tired and gonna go get it checked out....Anyone have anymore suggestions....

2003 400EX
WB E-series slip-on
K & N air filter w/outer wear
no air box lid.
stock jets...