2004 CR250 carb swap

jake_mullins
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jake_mullins
I have a 2004 cr250 and I'm wanting to put a keihin pwk38. I know I need the short body (75mm) carb, what I dont know is what carb is the easiest to swap, whether a carb off a YZ or KX or even an RM requires the least work. I know the yz use the power jet, also will I need a new throttle cable. All help is appreciated. I know there's a lot of threads over this but I can't find exactly what I'm needing to know.
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adam8781
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adam8781 1/18/2017 9:46am
1/18/2017 9:46am

newer yz250 carb, 02 and up is a direct drop in (both are 75mm long) theres a guy on thumpertalk that makes a pigtail harness to hook up the wiring in the yz carb to the cr.

or the older screw top type (2000 cr250) is also a great drop in but you cant run the tps. the good news is many people dis connect it anyways (including factory honda back in the 2 stroke days)

the tmx is shit stock but has alot of potential, consider sending it to rb designs, he can make the stock carb sing with his bore, mods and power wing.
digger
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digger 1/18/2017 9:49am
1/18/2017 9:49am Edited Date/Time 1/18/2017 9:50am
jake_mullins wrote:
I have a 2004 cr250 and I'm wanting to put a keihin pwk38. I know I need the short body (75mm) carb, what I dont know...
I have a 2004 cr250 and I'm wanting to put a keihin pwk38. I know I need the short body (75mm) carb, what I dont know is what carb is the easiest to swap, whether a carb off a YZ or KX or even an RM requires the least work. I know the yz use the power jet, also will I need a new throttle cable. All help is appreciated. I know there's a lot of threads over this but I can't find exactly what I'm needing to know.
Your best bet,would be to get a carb off a, 00-16 YZ250 or one from a 01-08 RM250. The KX carb uses a different top with a swivel. This carb will require a different cable, or you having to drill out the swivel and add threads. Either carb you choose will require that you use the cable guide(the small brass part that screws into the top of the Mikuni carb) on the Keihin. Your stock throttle should work. I routed mine down the right side. Just so that you know, Every RM carb that I have worked on has spec'ed out to be 1mm larger than the YZ and KX carbs.

On any of the carbs that you get the power jet, located under the plunger itself, will have to plugged. You can either buy the correct hex head plug, I forget the size at the moment, or you can unscrew the power jet,and plug the small hole with solder or quick steel and screw it back in. Either way will work fine, but it must be plugged.

You can either choose to use the TPS or not. It doesn't fell that much different when left unplugged. You may not even notice a difference.

don't be afraid to ask if you have other questions.



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jake_mullins
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jake_mullins 1/18/2017 2:00pm
1/18/2017 2:00pm
digger wrote:
Your best bet,would be to get a carb off a, 00-16 YZ250 or one from a 01-08 RM250. The KX carb uses a different top with...
Your best bet,would be to get a carb off a, 00-16 YZ250 or one from a 01-08 RM250. The KX carb uses a different top with a swivel. This carb will require a different cable, or you having to drill out the swivel and add threads. Either carb you choose will require that you use the cable guide(the small brass part that screws into the top of the Mikuni carb) on the Keihin. Your stock throttle should work. I routed mine down the right side. Just so that you know, Every RM carb that I have worked on has spec'ed out to be 1mm larger than the YZ and KX carbs.

On any of the carbs that you get the power jet, located under the plunger itself, will have to plugged. You can either buy the correct hex head plug, I forget the size at the moment, or you can unscrew the power jet,and plug the small hole with solder or quick steel and screw it back in. Either way will work fine, but it must be plugged.

You can either choose to use the TPS or not. It doesn't fell that much different when left unplugged. You may not even notice a difference.

don't be afraid to ask if you have other questions.



Thanks for the reply!
So after I get the carb and plug the power jet, what else do I need to do get everything correct. Aside from routing the throttle cable, and mounting the carb itself and of course jetting.
cable
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cable 1/18/2017 3:44pm
1/18/2017 3:44pm
I used one off a kx500. 39mm or 40. I thought i had the older one jetted pretty good, but this setup stepped it up a notch. I still have it and use it on a cr500 ice bike now.

The Shop

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digger
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digger 1/18/2017 4:02pm
1/18/2017 4:02pm
jake_mullins wrote:
Thanks for the reply! So after I get the carb and plug the power jet, what else do I need to do get everything correct. Aside...
Thanks for the reply!
So after I get the carb and plug the power jet, what else do I need to do get everything correct. Aside from routing the throttle cable, and mounting the carb itself and of course jetting.
Nothing, Put your jetting in there and go.

Here is a link to all of the vent hose that you will ever need, and then some.

http://www.motosport.com/oem-parts/part-number/95003-07008-60M?mmysourc…
jake_mullins
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jake_mullins 1/18/2017 4:24pm
1/18/2017 4:24pm
digger wrote:
Nothing, Put your jetting in there and go. Here is a link to all of the vent hose that you will ever need, and then some...
Nothing, Put your jetting in there and go.

Here is a link to all of the vent hose that you will ever need, and then some.

http://www.motosport.com/oem-parts/part-number/95003-07008-60M?mmysourc…
Appreciate it big time.
bronwynrayne
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bronwynrayne 1/18/2017 10:19pm
1/18/2017 10:19pm
I'll get old man Watson over here to help you out in the morning.

He's the carburetor king.
bronwynrayne
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bronwynrayne 1/19/2017 8:32pm
1/19/2017 8:32pm
"Any of them will work, you'll just need another throttle cable..."

A throttle cable is like twenty bucks, and I'm a girl and I could replace that thing in like five minutes. Just get whichever one you want, from the list I have provided below. Our livingroom committee suggests the YZ one for starters. Actually, my roommate suggests you do a fuel injection conversion.

Found this for you:

Bikes with PWK Air Stryker (variations for some years so do research):
’01 and newer Yamaha YZ250 w/TPS
’98 and newer Kawasaki KX250 w/TPS
’98 and newer Suzuki RM250 w/TPS
’99-’00 Honda CR250 long-body w/out TPS
’02 and newer KTM 2-strokes (some are the Air Striker, while some are the standard PWK, as well as 36mm)

You can tell which ones are the Air Stryker by two fins on the inlet side. I am literally copying this crap verbatim from some other site so take my advice at your own risk.

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