Jetting help.

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19Delta
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Jetting help.

Post by 19Delta »

Sorry, I know there is a lot that goes into this, but I'm in the garage wrenching, and don't have a lot of time to research. I know there is a thread of how to properly jet bike, but it is 20 outside, with a bunch of ice and snow, so no riding, and I'll be riding when its warm, and I'm just trying to get in the ballpark to get the bike to run decent enough to drop off at a shop next week to have suspension gone thru, and have them jet bike properly. (I trust this guy at the shop 100%, but how do they jet and tune bikes? Do they have some special way other than throttle chop? Seems like that takes a lot of time.)

What I have (new to me recently, so haven't ridden more than 20 min total):
97 KDX 200.
Gnarly pipe, and some aftermarket silencer.
Dual stage boyesen reeds, with stock cage.
RB carb designs carb modified.
Stock head (according to PO)
I'm in Northern Indiana, about 850' elev'.

RB designs paper work came with the bike. He put in it (and I verified that's what is in it when I cleaned carb, as PO left bike sit for 3 years after he drained the gas):
150 main
40 pilot
Clip is a CEK, set in middle (3rd slot).
Starts super easy. Idles fine. Yes, I have played with the RB air adjuster per instruction.

Problem:
Doesn't want to rev quickly (bogs instead) from bottom to about half way up. If I work it up slowly/med pace, then hit it, she runs like a rapped ape on the top end. (I always wondered why rapped apes run so fast, never have seen it in person yet) :boogie:

I put my sons 03 stock kdx carb on it, and it runs better, but nothing like it should. I don't know what his bike is jetted at, but the PO did jet his, and his bike runs GREAT. It is ALL stock. Looks almost new.

Again, just trying to get in the right ball park.
Thanks guys!
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19Delta
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Re: Jetting help.

Post by 19Delta »

Here are some pics of the plug that came in the bike. No idea how long it was in there. Image
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19Delta
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Re: Jetting help.

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Tedh98
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Jetting help.

Post by Tedh98 »

19Delta wrote: Problem:
Doesn't want to rev quickly (bogs instead) from bottom to about half way up.
Is it a lean or rich bog?
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19Delta
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Re: Jetting help.

Post by 19Delta »

Honestly, I don't know how to tell. How?

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Tedh98
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Re: Jetting help.

Post by Tedh98 »

19Delta wrote:Honestly, I don't know how to tell. How?
I pulled this from another site:

"Lean in a hollow "buuuuhhhhwwaaa" bog. Think hound dog or wolf howling... Anyone who's ever left the gas tank valve off has heard the lean bog....

Rich isn't so much of a bog, it's more of a stutter"

Hopefully you can picture that in your head.
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Julien D
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Re: Jetting help.

Post by Julien D »

Id play with the needle first. drop the clip down a notch or two to raise the needle and allow more fuel and see if it is better or worse.
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Re: Jetting help.

Post by kaw814 »

I'd start with the pilot or neede...it looks like its running hot by the looks of the plug. Start in small increments..throttle response will tell you if you're heading in the right direction.
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Jetting help.

Post by ohgood »

start with a clean air filter, it's key to good jetting.

warm it up normally, then pull the air box lid off and rub it again. if it's better, you're rich. if it's worse, you're lean.

there is a jetting guide on this forum that takes your through it step by step. it works, give it a read. :-)
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19Delta
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Re: Jetting help.

Post by 19Delta »

ohgood wrote:start with a clean air filter,

then pull the air box lid off and rub it again.
Filter is clean.

Rub it? You really LOVE your KDX huh?

(Lol, just joking, I know you meant "run" it again) I'll give that a shot when it warms up next week. I currently don't have an air box lid on this bike, but I can borrow my son's.

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Tedh98
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Re: Jetting help.

Post by Tedh98 »

So is it a lean bog?


For what it is worth - when I had a 200 I used a 155 main,40 pilot and a DEK on the 2nd clip from the top. I ride 700-1000 feet elevation. RB carb and head, PC2 pipe and 607 reeds.

I know your problem is down low, but the 150 main seems lean. But every bike is different. Going through the complete jetting process is the only way to get your bike properly set-up.
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