Jetting for a White Brothers E-Series full system?

[Zhutch7]

I am getting a 2002 400EX today and the guy told me when it gets into 3rd it bogs down and something hits the choke and turns it on? I am not 100% on the information here. I believe that is what he said. It has the WB E-series full system and Wiseco piston that is 5 thousandths over stock bore. I need to have this fixed ASAP. Will a 155 main jet and 42 pilot do the trick? I live in Arkansas and around this area is where I will be riding the most. Any help will be appreciated.

[DragonGunner]

How is changing jets going to stop a faulty choke? Something is wrong if the choke is coming on....thats causing the bog.....fix the choke, or take it off and go with the bigger pilot.

[JOHNDOE83]

160-42 remove choke.

[Zhutch7]

JohnDoe, how do you know exactly which one to go with? Why 160 & 42?

[Skeldaw]

Do you have a K/N or UNI?

[DragonGunner]

Your jetting depends what you have for air flow...closed lid, stock air filter, open box, K&N filter, lid with holes in it.....jetting can be from 150 to 190 or even higher.....closed airbox with stock filter....160 or 165 is a good start with your exhaust....42 pilot just helps it start alot better.

[Zhutch7]

I'm sorry if the previous posts sounded dumb. I'm young and I am trying to learn these things. I'm new at this, so please bear with me. It has a stock air filter in it now, but I plan to get a K&N sooner or later. I will have the air box lid closed.

[JOHNDOE83]

that jetting isnt exact, but it will get you up and running with no issues and decent reliability.

you need this web site www.jetsrus.com

read the FAQ section.

for main jet tunning you go all the way big on main jet until it stutters on the. top end, then bring jet sizes down till you fully rev out. thats the only way to perfectly tune your main jet

42 pilot is for stock carb 50 pilot for 450r carb, there is no need for exact tunning of the pilot jet. these are all your ever gonna need.

needle generally stays the same in the middle position unless you have a mid rpm hesitation or bog.

If this is to complicated for you right now then go with what me and dragon reccomended and you will be ok.

[Zhutch7]

Alright great. I appreciate it very much! We are doing a complete restoration on the quad. From the frame up. And my dad has his own powder coating business, so that's a plus for me lol.

[Zhutch7]

I am buying a regular K&N air filter today. It's not the full kit, just the filter. Is it going to need to be jetted differently than what you both have told me already?

[JOHNDOE83]

should be ok.

This is just a decent ballpark estimate to get you up and running safely and not to worry about jetting for now.

In the future, you will wanna start experimenting or adding more mods.

Then you will need the info in that website and more jetts, until then throw a 160 main and a 42 pilot and have fun.

Wear a helmet.

[Zhutch7]

Okay thanks!

[Zhutch7]

One more thing. What about the needle, and the a/f screw?

[Zhutch7]

And should I get dyno jet kits

[JOHNDOE83]

The needle in stock position is generally ok for all mods. in some cases it has to be richend up or leaned slightly. "But not often"

The a/f screw generally should be 2.5 turns out.

A 42 pilot and 2.5 turns on the a/f screw should make almost any 400ex motor start wothout the choke. Just pump the throttle a few times and it should start right up even in cold conditions.

At most you should only go 3 turns out on the a/f screw.

Dont buy dyno jets.

Go to www.jetsrus.com and buy the right jets

[Zhutch7]

Okay great. God Bless!

[Zhutch7]

Every time I try to order or put the jets in my cart it automatically puts the carb rebuild kit in there. Do I need that? Or the "jet kit" individually? Or do I just need the 160 main and 42 pilot

[riley1374]

I have a feeling your going to need bigger then a 160 main, and no, you do not need the rebuild kit. I would think you should be around 170ish.

[Zhutch7]

Why 170 you think?

[riley1374]

We have similar mods and I am running a 180 at sea level. 170 was too lean for me.

[Zhutch7]

Alright, I will order a 170 too. 42 pilot?

[riley1374]

Yep 42 pilot good for any 400ex. I tried the 45 and too rich.

[Zhutch7]

Okay great. Thank you! God Bless!