Carb question for the experts...

Questions and Answers about the best carb and Head mods available for the KDX.
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B737driver
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Carb question for the experts...

Post by B737driver »

04 200 with the RB modded carb and head mod and the other standard stuff pipe etc..

Bike runs really, really good on the low end, but sometimes when going from idle to WFOT there is a hesitation, bog if you will. I mx'd the bike a bit the other day and it was very apparent. After landing from a jump for example (idle) to WOT the hesitation was enough to get your attention when you expect the bike to accelerate, and it does the opposite.

The carb is setup just as I received it from RB.
Mixture Screw setting 7/8 out
Needle/Clip position CEK-3
Pilot Jet 40
Main Jet 152

He did supply alternate jets (38 & 42) and (150 & 155) just not sure which way to go with it.

I must say that I'm not that well versed in carb tuning. Any help is greatly appreciated.

Thx,
Don
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doctord23
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Re: Carb question for the experts...

Post by doctord23 »

Bog usually means lean.
I suggest that you try a bigger pilot (42) first, then the clip position.
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B737driver
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Re: Carb question for the experts...

Post by B737driver »

From what I've read that makes the most sense. It was colder than normal the last time I rode which adds to the lean condition. It also would bang and pop from time to time at WOT coming out of corners when slipping the clutch. Think I'll try the bigger pilot next time out.

Sorry for the ignorance, but what impact does needle clip position have?
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ICRage42
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Carb question for the experts...

Post by ICRage42 »

Now, it's time to work on the needle. Mark the throttle grip at 1/4 and 3/4

openings. Ride the bike between these two marks. 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.


This is from indawoods jetting guide. This what your asking?
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Carb question for the experts...

Post by Slick_Nick »

The needle generally has more to do with the delivery of fuel at a certain time, vs how much, although it does control how much comes from the pain.

Have I confused you yet? :shock:
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B737driver
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Carb question for the experts...

Post by B737driver »

Thanks Rage, Dr, and Slick....Starting to get a better grip on the jetting issue. Planning on going through the entire jetting guide at some point, just need a little time for uninterrupted reading.

I haven't changed anything yet, rode briefly today (70 degrees outside) and the hesitation was not as apparent as before, but still there.
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