400ex jetting

[JoE4554]

whats a good place to start with the jetting for a 400ex carb on the 300ex?? My 300ex has a full W/B exhaust , k&n filter , no lid. And i did do a search. Any help would be great...

[2muchquad]

Try a 40 pilot and a 148 main for starters,i think thats what i had when i ran a 400ex carb.;)

[JoE4554]

what notch should i put the clip on??

[2muchquad]

try it where it is for starters,you may have to lower the clip(raise the needle) though;)

[250X_project]

what would You say for the 406 in my sig?

[2muchquad]

Try a 142 or so for starters,your biiger motor will actually require leaner jetting:D

[250X_project]

wow another guy told me to start at a 180 :eek2:

[250X_project]

Now that I think about it how could it be that lean. 148 is stock for a 400EX carb. Comparatively I have the same stroke, and bigger bore. full exhaust, K&N filter, no lid, no choke. That's a lot of air. Plus the cam and port job with bigger valves. wouldn't that need more fuel not less?

[JoE4554]

which one is a 40 pilot in a dynojet kit?? it doesnt say

[250X_project]

Dyno-jet kits only have main-jets and are labeled as to which is which.

[JoE4554]

so what should i do since i need a pilot?? it might sound like a stupid question, im not that filmiliar with jetting

[250X_project]

Naw no problem just go to your local dealer they are only about $4-$5

[JoE4554]

oh ok....ba wha others sizes should i get because i dont wanna make 10 trips jus for one little pilot

[250X_project]

I hear ya. Depends what you running now? not starting well? Removing choke?

[JoE4554]

well i havent installed my 400ex carb yet. Well i was told to start at a 148 main and thats what the stock main is as you said above. Ill be running choke, i have a full exhuast , k&n filter and a rev limiter as far as motor mods.And are all 40 pilots the same or is each one different for each carb??

[250X_project]

With full exhaust, filter and even with the box lid removed 148 would be rich, yet always start rich. What's the smallest jet you have? If you are running choke I would get the 40pilot and stay at that. If starting problem occur later than maybe you would want a 42, but I doubt it.

As far as are the jet comparing I don't know to be honest with you.

[JoE4554]

i think the smallest jet that comes in the kit is a 136 or sumtin like that

[bwamos]

Start with the stock 400ex jetting. It actually shouldn't be too far off.

I'm running a 160 main w/ 42 pilot on my 400ex carb on the 330.

On the 300ex carb I was running a 135 main, and a 42 pilot.

Since a full exhaust, k&n filter, and no lid runs about a 128 main, 40 pilot deductive reasoning would put the jetting near the 400ex stock jetting (148) w/ a 40-42 pilot.

Mine didnt' want to idle with the stock 38 pilot after letting the choke out.

[250X_project]

Hey thats good to know. what would you suggest with mine with mods listed running a 400 carb? I have a 175 that came with my carb.

[JoE4554]

now that i know a stock jet is 148...i kinda wish i didnt spend 60 bucks on it....ba i got it anyway...i just calld my local dealership and they said they have a 40 pilot....ill either go 2night or tomorrow...i also get a 42 pilot....all i need is for my carb to get in...when it gets in....ill let you know how it runs

[250X_project]

Either way you have a nice looking quad, I give her the thumbs up.

[JoE4554]

THANK YOU....ill post up new pics if i can get my digital to work....i need this carb....my cuzin gave me some competition with their 390's...i kno it wont be as quick as them, but hope this will up the ante on the track....oh yeah...what throttle cable should i use....400 or 300??

[250X_project]

That's a good question, I still need to figure that out, come to think of it. lol...what's everyone else using?

[bwamos]

300ex/250x throttle cable fits up perfectly to the 400ex carb. The only thing that isn't a perfect fit is the intake boot. Required a LOT of stretching.

[250X_project]

Yeah thats what I've heard. Thanks.

JoE4554- I think I left you a PM, if not I will