KDX Jetting Database (complete)

A reference for the PWK carbs...
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Jaguar
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KDX Jetting Database (complete)

Post by Jaguar » 06:55 pm Jan 07 2019

Every jetting database on forums I’ve seen so far lacked essential data such as weather data which can make a huge change in jetting needs. Also whether or not the gasoline has ethanol and at what percentage (it should be listed on a sticker on the gas pump). I consider every detail important because they all figure into the final mix. I just made a jetting calculator which shows a graph of the jetting all through the throttle settings. Too rich is above the 1.0 line, and too lean is below the 1.0 line. So I’d like to start a new database here for KDXes and after a handful are submitted I will post the calculators results for each data set, showing how rich/lean it is at half throttle and 7/8 throttle. I will make needle recommendations also. So here is the info needed. Please don’t submit unless all the info is filled in. thanks
engine cc:
carb size:
fuel/oil ratio:
% ethanol in gasoline:
standard or modified snorkel:
pilot jet:
needle ID:
clip position (1-5. 1 is at top):
main jet:
slide cutaway (I think 5mm on '95 and newer and 6mm on all others):
feet elevation above sea level:
% relative humidity:
fahrenheit temperature:
Performance CDI -- KDX motocross mods -- the SR KDX -- expansion chamber analysis---> http://www.dragonfly75.com/moto/

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Re: KDX Jetting Database (complete)

Post by Jaguar » 08:44 pm Jan 07 2019

If your jetting best suits a certain type of weather then use those weather details.
How these details affect jetting:
Higher elevation, higher humidity and higher temperature all cause richer jetting (requiring you to install smaller jet sizes).
More ethanol causes leaner jetting (requiring larger jets)
Performance CDI -- KDX motocross mods -- the SR KDX -- expansion chamber analysis---> http://www.dragonfly75.com/moto/

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Re: KDX Jetting Database (complete)

Post by John_S » 02:23 pm Jan 08 2019

Thank you for helping out with jetting. As my bike sits now

2002 220
RB head
35 air striker
Vforce reeds
FMF woods and Turbine Core 2
40:1 Honda HP2
1/3 110 octane, 2/3 90 octane recreation fuel (non ethanol), both Chevron
Air box lid and snorkel
40 pilot 1.5 turns out
JD red 2nd clip
145 main
4.5 slide
Sea level
77 degrees, 63% humidity

This set up is responsive and has very little spooge, none dripping but black and a little tacky inside the end of the silencer. Clip 3 or a 150 main would both sputter rich and drip spooge

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Re: KDX Jetting Database (complete)

Post by Jaguar » 03:17 pm Jan 08 2019

here's info from JD Jetting:
The needles in the KDX jet kits are in the same range as CEK/DEK single taper needles, but ours are custom machined triple tapered needles. They are precision machined and give a more even flow of power than standard needles, but do not get excessively rich like N85D type needles. There are 2 needles in the kit, which span either side of CEK/DEK with slightly richer and slightly leaner straight diameters. The Blue marked needle is for lower elevations and cooler temperatures (richer), and the Red marked needle is leaner on the straight diameter for warmer conditions or slower paced riding, but not excessively. Yes, these are special needles, as I've spent years developing and refining the taper angles and lengths to make them perform in varied conditions without being as sensitive to changing weather and temperatures compared to stock needles. The needles will work well with the RB modified carburetors.
Performance CDI -- KDX motocross mods -- the SR KDX -- expansion chamber analysis---> http://www.dragonfly75.com/moto/

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Re: KDX Jetting Database (complete)

Post by Jaguar » 07:47 pm Jan 09 2019

these special needles don't have published dimensions so I can't analyze it on my calculator.
Normal PWK needles I can find their dimensions.
Performance CDI -- KDX motocross mods -- the SR KDX -- expansion chamber analysis---> http://www.dragonfly75.com/moto/

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Re: KDX Jetting Database (complete)

Post by SS109 » 10:49 pm Jan 10 2019

Someone with the JD needles should measure them on a good set of calipers and post up the specs.
AZ State Parks OHV Ambassador - Trail Riders of Southern AZ
'11 GasGas EC250 Race
Current KDX: '98 KDX220
Old KDX: '90 KDX200 -White/Blue

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Re: KDX Jetting Database (complete)

Post by John_S » 07:36 am Jan 11 2019

Jaguar I've switched from the JD red to the CEL enough to know that all the settings I listed above would be the same if I used the CEL on clip 2 instead of the red needle on clip 2. Would you be able to work with that?

SS if I had a good set I would check but the ones I make due with are definitely not a high quality tool.

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Re: KDX Jetting Database (complete)

Post by Jaguar » 09:11 pm Jan 12 2019

Probably not because having precise dimensions are important. The red needle is a triple taper which is very unusual. And the air striker has a different kind of slide. My calculator expects the slide to be somewhat normal.
Performance CDI -- KDX motocross mods -- the SR KDX -- expansion chamber analysis---> http://www.dragonfly75.com/moto/

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Re: KDX Jetting Database (complete)

Post by Jaguar » 03:33 pm Jan 13 2019

Here’s my new videos:
About 2 Stroke Jetting
Jetting Calculator Spreadsheet
Performance CDI -- KDX motocross mods -- the SR KDX -- expansion chamber analysis---> http://www.dragonfly75.com/moto/

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