Carb Help!!!!!!!!!!

[chad400ex]

Okay, I put in the Dynojet Jet Kit (stage 1) followed the directions exactly with the needle clip position (it's 3 down from the top). I put the dynojet 146 main jet in, and turned the fuel air screw out 3.5 turns. I'm running with the stock airbox lid, K&N filter, and a Yoshi Slip-on pipe. I'm getting a little stutter in the initial throttle response, and when I rev it and let it come back down to idle it backfires, but not very bad (just a little "miss" I guess). I'm thinking that I'm too lean. I'm going to rejet tomorrow. I think I'll go up one size on the main to a 150, or maybe 155. Do you think the fuel/air screw is in the right spot, or should I back it down to 3. I ride mainly at sea level to 3000 ft.

[VegasEx'r]

You're way lean. I know that the Dynojet instructions say to do the stage 2 setup only if you aren't using the airbox lid, but I would try that. Stick the 170 in there like they say & let her rip. You might want to try a bigger pilot (like a 40). But get the lean pop fixed first.

[Atomic83]

170 would be rich if you have the stock airbox lid. 150 or 155 would be about right, stick them in and see how it runs.

[01_300ex]

what size is a stock 400ex main jet. Because i just bought a 400ex carb for my 300ex and it has a 160main jet in it, and it is running a little lean.(backfiring when i slow down).

Hey I have a 01 400 EX and I plan to do exactly what you have done. I have a full Yoshi Stainless System on the way and i plan to put the K & N Filter on and the Dyno Jet Kit. Once you get your carb right will you let me know how your EX is running. I want to know if I do these 3 things if there will be any problem or how much of an increase in power you get.


Thanx

Brad

[MIKE400EX]

You'll probably need a 150-155 min jet. But first put a #40 pilot/slow jet in there. Your (carbs) problem sounds like idle/off-idle not the main circuit.

[chad400ex]

Once I get it set up right, I will post it on this thread. I think it's really close right now. I also bought the T.E.C. endcaps for my pipe, so if I need to go quiet, I can change out the endcap on my pipe in like 5 minutes. This also seemed to help the bike run better than a fully open pipe w/ spark arrestor. That's how I decided that I was running lean. A smaller exhuast opening = less air flow, which will fix a lean condition. But for now, I'd rather have it jetted for the Yoshi pipe without insterts. It should work out. Changing the main jet is simple. All ya gotta do is loosen the carb boots clamps and rotate the bottom of the carb to the left side of the bike. Instant access!!

[Wheelie]

The 'pop' you're experiencing is caused by the slow circuit. Before you change the main jet, step the pilot up to a #40.

I'm not sure what the differences are between dynojet #'s and keihin #'s, for keihin jets and your setup a 150 or 152 main jet should do the trick. If you decide to remove the airbox lid, a 155 or 158 will cover your engines fuel needs.

Good Luck!

[PoopOna400EX]

The stock jet on the 400 is a 148. I would bump up to between a 150 and 155 as mentioned. I would also recommend bumping up the pilot. The stock is a 38, I would look at trying a 40 pilot. In any case, it's all it what seems to work best.

As far as the Pilot Set Screw, I would put it at a 2.5 - 3 for starters. This is something you can adjust after everything is running, and will mainly just effect the idle RPM. Set it at what you think, then adjust it later to perfect the setting. (Adjusting it later is a beast of a job, but you can do it with a small flat head screw driver. You'll probably get a hand cramp too!)

Good luck,

~Jason

[chad400ex]

Well....I put in the Dynojet 155 main jet. It seems to be running good now. I'll know for sure after I ride at sand lake tomorrow. Thanks for the advice guys:)