Need a new carb for your KX500?

Dirt Bike Technical discussion. This is for a little more in depth discussions :-)
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Sandblaster
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Need a new carb for your KX500?

Post by Sandblaster » Sat Apr 29, 2017 3:43 pm

Need a new carb for your KX500?

Looking at Adam MillAr's flow bench numbers and info gathered from Kawasaki Team Green Mechanics we have come up with the following..

96-97 KX250 or a 2000 Cr250 carb.
Or you can go to Sudco and get a Keihin Quad vent Air striker 38mm for about 200.

You can use the newer Airstrikers as well but you need to block off a few things.

It will add 1 hp to the rear wheel on a completely stock KX500.. That is dyno confirmed.

The flow bench shows that it does just as well as a 41mm Airstriker for volume and velocity. That is also dyno confirmed...

We need to come up with some decent jetting specs.

Sean Colliers bike.
pilot 55
main 175
16009-1613 NEEDLE-JET N89D - 2nd position
Slide 7

We ran this at Glen Helen 1700-1800 ft.. 50% C12 and 50% 91 California pump gas.

You will need the correct throttle and cable for which carb you choose.
If bikes are for kids I'll never grow up.

moto939
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Re: Need a new carb for your KX500?

Post by moto939 » Mon May 01, 2017 3:55 am

Thanks for the info.

Do you know the difference between the N89D needle you used and the stock N82M needle?

Once it stops raining and snowing around here, I plan to get some actual time on the bike and figure out the jetting with the stock carb. Once I get a baseline and a good feel for it, I try a short body A/S from a YZ250 (powerjet blocked off). I also have a #8 slide I might try if time permits.

Basic specs

Bone stock motor
Rad valve with spacer
1600 ft
50/50 VP110/non ethanol premium

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Sandblaster
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Re: Need a new carb for your KX500?

Post by Sandblaster » Mon May 01, 2017 5:32 am

The N89D fattens up the midrange.
Most of the guys are experimenting with richer slides and leaner jetting..
I think in the 5 range....
I have only ran the 7
I want to try a short body version....
If bikes are for kids I'll never grow up.

moto939
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Re: Need a new carb for your KX500?

Post by moto939 » Mon May 01, 2017 7:31 am

Good info....I have to remind myself, what works in a 250/300 doesn't necessarily work in a 500. I've got a #6 slide kicking around somewhere.

Too many variables, not enough time! :D

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Sandblaster
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Re: Need a new carb for your KX500?

Post by Sandblaster » Mon May 01, 2017 2:02 pm

Isn't that the truth... I could play with my toys all day long if I didn't have to work... :shock:
If bikes are for kids I'll never grow up.

kyser777
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Re: Need a new carb for your KX500?

Post by kyser777 » Wed Jul 26, 2017 11:38 pm

I heard that there is different version of the 250 pwk38 (long and short)
First of all, is the pwk 38 air striker from a kx250 1996 is the same as the one on a kx250 1997?

I want to use it on a 1999 kx500, with a boyesen rad valve and spacer.
what about the clearance?
do you thing this pwk38 air striker is an upgrade compare to the stock kx500
carb, what will be the benefit?

On Sean Colliers bike, did you set the pwk38 with a boyesen rad valve and spacer?

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Sandblaster
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Re: Need a new carb for your KX500?

Post by Sandblaster » Thu Jul 27, 2017 3:45 am

First, welcome to the forum.
It's a lot easier to answer here then on eBay :lol:
Plus, I can point others to the answers when they ask :D

There is a long and a short version.
The newer versions are about 1/4" shorter then the older versions.
The issue is they have a throttle position sensor as well as a solenoid valve which require electrical connections to the CDI to work correctly. And, the KX500 does not have them.
However, I'm working on one right now to run on the KX500 for testing so stay tuned :geek:

Is the 96 and 97 KX250 carbs the same?
They are very close.
I have only tested the 97 so I don't have a comparison for the 96 but they should be very close.
There are a lot of sellers on ebay claiming that they are selling a 96 or 97 KX250 carb when they are NOT!!! :x
Same goes for the 2000 CR250... It's very irritating..
But how can you tell?
The 96 KX250 carb will have the following ID on the side: KEIHIN PWK G202
The 97 KX250 carb will have the following ID on the side: KEIHIN PWK G279
The 00 CR250R carb will have the following ID on the side:KEIHIN PWKC03ANJ

Spacing.
We are running a Boyesen reed with 10mm spacer on Sean's bike.
No modifications required.
However, we want to run a VF2 with 10mm reed spacer because the VF2 is a superior reed... But Sean has sponsors that we must stick with.

Performance increase?
Yes, the carbs above will net you 1hp increase to the rear wheel dyno proven.
Further, you will get faster throttle response.

Any other questions?
Feel free to post them up.
If bikes are for kids I'll never grow up.

kyser777
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Re: Need a new carb for your KX500?

Post by kyser777 » Fri Jul 28, 2017 1:54 am

for a new carb

the 2000 cr250r fit without any additional parts?

if I buy a new pwk38as, is this the right model?
16100-KZ3-J21
16100-KZ3-J22

about jetting
175 for the main jet / 55 pilot (for the Sean collier kx500)

I thought that combined with a rad valve we need to lean the jetting

for a stock cylinder and head , this is what you recommend?
I am under 1000m of elevation

does the PWK38AS give more low end ?

thanks

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Sandblaster
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Re: Need a new carb for your KX500?

Post by Sandblaster » Fri Jul 28, 2017 5:04 am

Whether you use the Honda or Kawi PWK Air Striker you will need to use the throttle and cable from the corresponding bike.

16100-KZ3-J21 is correct. It's a 00 CR250R carb

Jetting..
Sean's engine has been highly modified.
He runs race gas.
And, his racing altitude is higher then yours.
You may or may not need to lean the jetting.
I don't remember the specs from the dyno runs with the stock engine so I will need to check on that.
Remember... Jetting specs should be considered rough guidelines..

Yes, you will get more power everywhere with the new carb..
If bikes are for kids I'll never grow up.

kyser777
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Joined: Wed Jul 26, 2017 4:31 am

Re: Need a new carb for your KX500?

Post by kyser777 » Fri Jul 28, 2017 6:25 am

thanks a lot!!

regarding the Throttle
do I have to get the oem 2000 cr250r cable (17910-KZ3-J20 , part obsolete)

I found on Xbay a Motion Pro Vortex Throttle & Cable CR125 93-03, CR250 90-04, CR500 90-01
this can be fitted?
it seems to be a generic part for honda 2 stroke mx bike, but not sure

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