Throttle Hesitation

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kdxdad
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Throttle Hesitation

Post by kdxdad »

Just installed a new FMF Woods pipe on my son's '03 220. Kept the stock can on. Now we have a slight hesitation from idle when I pin the throttle. If I slowly roll on the throttle, it runs fine. Otherwise, the bike rips now. I kept the stock jetting setup and the air screw is at 1.5 turns. Any suggestions would be appreciated.

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krazyinski
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Post by krazyinski »

try changing the clip position on the needle to 2nd from the top.
2000 KDX220 FRP Ported,plated cylinder,milled head, FRP bored carb, V force 3 reeds, FMF desert pipe, 10oz FWW, 98 KX forks and oem shock re valved by Pro Action, hyd clutch, fastway pegs, tall seat foam, gripper cover, 29" CRhigh mini bars, Cycra brush gaurds.
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kdxdad
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Post by kdxdad »

>|<>QBB<
krazyinski wrote:try changing the clip position on the needle to 2nd from the top.
So, are you saying it's too rich off idle, because the stock setting is the 3rd, correct?
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krazyinski
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Post by krazyinski »

thats what I would guess, the norm is to find youre base line pilot, main, and needle setting and tune to your riding conditions (temp and sea level) you might try removing the air box lid first. also try ajusting the air screw.
2000 KDX220 FRP Ported,plated cylinder,milled head, FRP bored carb, V force 3 reeds, FMF desert pipe, 10oz FWW, 98 KX forks and oem shock re valved by Pro Action, hyd clutch, fastway pegs, tall seat foam, gripper cover, 29" CRhigh mini bars, Cycra brush gaurds.
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kdxdad
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Post by kdxdad »

>|<>QBB<
krazyinski wrote:thats what I would guess, the norm is to find youre base line pilot, main, and needle setting and tune to your riding conditions (temp and sea level) you might try removing the air box lid first. also try ajusting the air screw.
From what I've read here, I was hoping I wouldn't have to re-jet. I'll monkey w/ the air screw. I've already cut a hole in the airbox lid. Thanks for your help.
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Indawoods
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Post by Indawoods »

I was thinking air screw or needle position myself. At least it doesn't cost anything but time eh? :wink:
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Post by kdxdad »

So, if the airscrew was 1.5 turns out, I should start turning it out more because I may be too rich. If I get more than 2.5 turns out, then I should change the clip position, correct?
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Indawoods
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Post by Indawoods »

"If your airscrew is less than 1 turn from closed, you need a larger pilot jet. If it is more than 2.5 turns from closed, you need a smaller pilot jet."

"If the bike bogs for a second before responding to throttle, lower the clip (raising the needle) a notch at a time until the engine picks up smoothly. If the bike sputters or sounds rough when giving it throttle, raise the clip (lowering the needle) until it runs cleanly. There isn't really any way to test the needle other than by feel, but it's usually quite obvious when it's right or wrong."


All taken from here:

http://www.kdxrider.net/forums/viewtopic.php?t=1156
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Post by thebleakness »

While were on the topic of needles, how do you know when it's too much? Say you found that the best position is the clip at the very top (position #1, correct?), this would make it richer, should you put in a larger main (or pilot) and re-adjust the needle again so that you have some more working room to fiddle with it?

The more and more I've been riding and fiddling with my bike this jetting stuff comes more easily but these kinds of questions come up from time to time.

Sorry for the Hi-jack. :butthead:
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Post by krazyinski »

>|<>QBB<
thebleakness wrote:While were on the topic of needles, how do you know when it's too much? Say you found that the best position is the clip at the very top (position #1, correct?), this would make it richer, should you put in a larger main (or pilot) and re-adjust the needle again so that you have some more working room to fiddle with it?

The more and more I've been riding and fiddling with my bike this jetting stuff comes more easily but these kinds of questions come up from time to time.

Sorry for the Hi-jack. :butthead:


its time for a different needle.
2000 KDX220 FRP Ported,plated cylinder,milled head, FRP bored carb, V force 3 reeds, FMF desert pipe, 10oz FWW, 98 KX forks and oem shock re valved by Pro Action, hyd clutch, fastway pegs, tall seat foam, gripper cover, 29" CRhigh mini bars, Cycra brush gaurds.
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Post by canyncarvr »

Standard air screw adjustment procedure (what works, not what's necessarily read someplace):

Generally, in one gear too high, under load adjust for best response.

Example:
2nd gear @ walking speed, adjust to NO hesitation when throttle is wicked from just off-idle to around 1/2 throttle.

Do not adjust the air screw to high idle speed.

Don't approach adjustment from the standpoint of, 'It's too rich, so I must have to turn it out,' or the opposite. Just find where it works..where the hesitation is gone.


This assumes other circuits to be in the ball park.


Re: "If your airscrew is less than 1 turn from closed, you need a larger pilot jet. If it is more than 2.5 turns from closed, you need a smaller pilot jet."

Not pertinent at this point...but remember this applies ONLY to un-modified (not RBd) carbs.

Re: 'I kept the stock jetting setup...'

Hardly ever correct. You will know when you determine it to be correct...or not.

Re: 'I was hoping I wouldn't have to re-jet.'

That's kind'a throwing the baby out with the bathwater........

THE best performance gain for the money is a properly jetted carburetor.

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Post by kdxdad »

Thanks for all the advice guys. I have a good base to start with now. I'll get started once it warms up around here.
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