carb/jetting help plz

[400thacker]

pre 04 400ex. Just bought this thing and it runs great if you hold it wide open or idling when you first start it. As soon as you put it in gear and start to take off it will barely stay runnin unless you hold it wide open.
mods are hotcam full white bros exhaust with K+N filter.

I just bought a moose carb kit and replaced everything. went from a 38/152 jetting to a 38/158 and it's all the same.
I have also tried the air/fuel screw both directions all the way with little to no effect.

currently 38/158 jetting with 3rd notch down on the needle and 2.5 turns out on the air/fuel mix.

installed a 300ex carb and the problem was fixed, it was just running real lean and popping real bad when i let off.

what am I missing?

any help is greatly appreciated.
thanks

[400thacker]

I forgot to mention that it's hard to start. like it's either getting way too much gas or not enough. but when i remove the breather tube and look i can see it squirting gas.

[Stickman400]

Try a 40 or 42 pilot, sounds like that's all you're missing. See if somebody else has some advice, I'm not the greastest with carbs.

[CJM]

To rich (in most cases but everywhere the elevation is different so it could be close), 155 is the highest I would suggest running in that setup.

1. Buy a 42 pilot. www.jetsrus.com

2. Buy GENUINE keihin jets from same website, moose or not I dont trust anything else to be accurate. You can keep trying to use the moose ones if you wish, I do not know the quality of them however and these carbs are PICKY!

3. The air/fuel screw (little brass screw on the outside of the bowl). Turn it all the way in GENTLY, then turn it exactly 2.5 turns out.

4. Needle is fine if its 3rd notch down from the flatend.

5. Check the idle, make sure its turned up to a reasonable level

Generally tho your problem is a lean pilot (these engines are jetted notoriously lean).

Also, change your plug after you jet it with the specs I mentioned. Then start it up and let it warm up and then run it wide open throttle in 3rd gear and hit the killswitch. Remove the plug, if its tan/goldish to chocolate brown its good. I myself like to be on the richer side just to be ok, so its ifs slightly black its ok as well-if its dark black, fouled, wet, nasty, etc then you need to recheck jetting.

[400thacker]

it runs the way it should with a 300ex carb on it and it only has a 122 main and a tiny pilot jet. i will try the rejet and see what happens.

[CJM]

Just cause it ran doesnt mean it ran well.

If anything you were VERY lean when you had that carb on there.

[400thacker]

i know it was running very lean but...atleast it would rev out instead of me having to pump the throttle constantly to keep it running unless i held it wide open.

any other ideas on what it could be? i have also ran it with stock exhaust and the WB full system and ran with and without the air box lid. still can't figure it out.

[CJM]

Carb could be sucking air, check the vent lines. Also theres a small screen iirc inside the carb where the fuel hose connects to-could be clogged.

What does the plug look like? Tan/gold, brown, black, wet, dry??