new parts, and cutout problems 400ex

[sleepin400]

Just installed a Wiesco 11:1 piston and a Stage 2 hotcam, and a mildly ported head (stock valve size)
It has a full yosh exhaust and (had) a 152 jet and ran fine.

It has a low end miss/hesitation, more noticable when in low gear (2nd or 3rd) and try to 1/2 to full throttle it up to speed. Higher rpm has much less if no miss problem. I will have to downshift too often to power up to speed to prevent cutout.

It was running with a 165 main jet and the stock needle movied down one notch.

I was considering moving the stock needle back to stock and putting a 168 in it. My friends has a close setup and run about the same.

Do you think this sounds right. What do you guys think?

also are all the jets numbering system the same. I was told that keihin jets are different? Anyone know about this.

any help greatly appriciated. I'm lossing races I shouldn't and have a hard time doing wheelies :(

[04hmf400]

It sounds as if you are jetted to fat on the main.There is a difference in the jet numbers.

[sleepin400]

I'm definitally not ruleing that out, But I woulda figured that it would cutout at high end as well if it was too fat??

I wonder if this needle is messing everything up.

Who has changed positions or replaced there needles on modded 400's?

thanks for the reply
anyone else have any ideas or similar situations?

[mojoe2878]

its sounds like you need to move the needle clip back to stock. since you are gettin more cut out from lower rpm and up and you say its better at the higher rpm, thats why i say move the needle clip because the needle is responsible for lettin fuel by up until you get to WOT and then its just comin straight thru the main jet, since your cuttin out before WOT,then i would think your needle is lettin too much fuel past when your at 1/4 or 1/2 throttle or whatever, your main jet is probably about right if it is clearin up in the higher rpms.

[XCR 440ex]

I would say that you should try changine the needle it's self because there is a noticable difference between the stock needle and a dyno jet needle (for example) and that little bit maybe enought to remove the cutting out. Also once your quad in warmed up trying using your choke if it is better with it engaged then you are too lean if your quad runs worse with it on you are too fat. as for the differences in jetting. kelin and macolliy (whatever the sp) are pretty much the same the main difference in in their installation one is slotted and the other is hex.