keihin pwk 36 vs 38


22 replies to this topic
  • market

Posted November 27, 2009 - 07:45 AM

#1

Hi, i' ve got a '04 cr125 with a 38 mikuni TMX, but i want to change it and buy a keihin PWK.....now i use the bike in enduro/woods riding..

Is better a 36PWK or a 38?

I've heard that with a keihin you will get more power at all rpm's, especially in the low-mid...

is a 36 too small?

Thanks!!!:excuseme:

  • ulmanb

Posted November 27, 2009 - 08:37 AM

#2

I like the 36mm in my cr250, but I think most 125's run a 38 or larger. Never heard of anyone running a 36 on a 125.

  • market

Posted November 28, 2009 - 07:21 AM

#3

ktm 125 (exc) has 36 pwk, and i think (but i'm not sure) that some cr's in the 90's had a 36...

I ask that because i want more power at low- mid rpms......

anyone else?

  • dmcca

Posted November 28, 2009 - 01:06 PM

#4

I have a 38 on my cr250 and it's the best mod I have done. A 36 will definitely give better low/mid power and should still give more than enough top end. If it were my 125 I'd go the 36 pwk

  • SlowSpokes

Posted November 28, 2009 - 02:49 PM

#5

I like the 36mm in my cr250, but I think most 125's run a 38 or larger. Never heard of anyone running a 36 on a 125.


Are you just running a standard PWK ?

From what I've heard, the pwk off the newer YZ's have a shorter body than the standard pwk's, and they fit a whole lot better. I've been trying to figure out if they make a short bodied 36mm.

  • gospeedracer51

Posted November 28, 2009 - 04:11 PM

#6

I've been trying to figure out if they make a short bodied 36mm.



The 36mm off a KTM is a short body (75mm). I think they use them on 200, 250 & 300's. I just got one from an '05 250 exc.

  • hallsy

Posted November 28, 2009 - 08:30 PM

#7

If you go with a KTM carb or any carb for that matter, make sure it's the one you want before you buy it. KTM used the longer body PWK's for years before switching to the shorter body PWK, and they have used the short body in both 36mm and 38mm versions. The shorter body is easily identified by it's top. It has a top thats retained by 2 screws, the longer body PWK's have a twist on top. Determining if it's a 36 or a 38 is a little more difficult. Not sure the following is totally correct but I think the 250/300 exc,xc,xcw got the short body 36mm in @ 04'. The 250sx got a 38mm short body in 03', then in 06' it changed to a 36mm. The 200xc,xcw didn't get the short body 36mm untill like 07', prior to that it was the old long body 38mm. The 150sx got a short body 38mm in 09. Again I'm not 100% sure about all that, but you can see how easy it would be to get the wrong carb if you don't know what your looking for! Don't count on the seller to know either, way to often i've seen carbs incorrectly advertised on fleabay. But it's easy to see why with so many of us switching out carbs. When the salvage man parts out my 01' CR 250 he won't know that I installed a 36mm PWK from an 06' KTM 250SX!

  • market

Posted November 29, 2009 - 03:30 AM

#8

first of all thanks to everybody.

I was talking about ktm's pwk but the one (used) that i've found is a 36pwk from a road bike....don't know if it is the longer or the shorter version, but that's not a big deal beacause normally with 2 stroke, if the carb is longer you have more low rpms, and if it's too long i can ''shorten'' ( ''cut'') with that,

http://www.cmc-to.it/images/fresa.jpg sorry but i don't know the enslish name.

but i don't think that because i' ve saw some riders that have put a spacer (moose racing) between the reed valve and the manifold....


probably if i install a 36 i have to install either a 36mm manifold, the standard is 38........??

my only indecision was that a 36 could be too small.........is that true?



Sorry for my bad english and thanks again!

  • ulmanb

Posted November 29, 2009 - 03:50 AM

#9

just for some confirmations:

My 06 200 KTM came with the long body 38mm. I beleive in 07 they switched to the 36mm short body.

My 06 300 KTM came with a 36mm short body.

On my 05 cr250 that came with a mikuni, I first swapped in a 38mm long body from a 00 cr250 (basicly the same as the carb from my ktm 200). I later installed a 36mm short body from a 06 300 KTM.

The bells of both the 36mm and 38mm were the same diameter, but the long body was about 1cm+/- longer than the short body. Not a real big deal, but the short body was nearly the same length as the stock mikuni making it a much better fit.

  • hallsy

Posted November 29, 2009 - 08:24 AM

#10

Ulmanb is right, the 36 and 38mm PWK carb outer dimensions are identical. My guess is both carbs start with the same casting. From my notes, the overall dimension of the PWK long body = 91mm, the short body is 75mm. The stock Mikuni TMX on the 04'-07' CR 250 = 76mm, stock Mikuni TMX for 01'-03' CR 250 = 85mm.

  • market

Posted December 01, 2009 - 07:07 AM

#11

thanks...

but i'm more interested about the size (36 or 38) than abouth the lenght....

if i go with a 36 have i to make a new manifold ???

thanks!

  • SlowSpokes

Posted December 01, 2009 - 06:00 PM

#12

if i go with a 36 have i to make a new manifold ???

thanks!


No, they will mount up the same. The only difference is the bore size.

  • jimbo1143

Posted December 23, 2009 - 07:55 PM

#13

Are you just running a standard PWK ?

From what I've heard, the pwk off the newer YZ's have a shorter body than the standard pwk's, and they fit a whole lot better. I've been trying to figure out if they make a short bodied 36mm.


The 99-01 kawasaki Kx125 have the short bodied 36pwk on them! I just bought one pretty cheap on ebay. They're identical to the 38pwk's that come on the 05 & newer Yz250's.Both have the TPS & Fuel cut silenoid. I cant wait to try it!!! :moon:

  • jimbo1143

Posted December 23, 2009 - 08:30 PM

#14

The 99-01 kawasaki Kx125 have the short bodied 36pwk on them! I just bought one pretty cheap on ebay. They're identical to the 38pwk's that come on the 05 & newer Yz250's.Both have the TPS & Fuel cut silenoid. I cant wait to try it!!! :moon:


Correction, The 36pwk short body carb was only on the 99-2000 Kx125. the mikuni tmx replaced the keihin in 2001.

  • motoxmann

Posted December 24, 2009 - 10:30 PM

#15

Don't count on the seller to know either, way to often i've seen carbs incorrectly advertised on fleabay. But it's easy to see why with so many of us switching out carbs. When the salvage man parts out my 01' CR 250 he won't know that I installed a 36mm PWK from an 06' KTM 250SX!


I agree completely.
That is why we decided to start keeping track of this exact information.
Take a look.
http://home.comcast....12-2009_all.htm
It's a little light on info but were adding more every day.

  • Redlined

Posted December 25, 2009 - 08:22 AM

#16

I agree completely.
That is why we decided to start keeping track of this exact information.
Take a look.
http://home.comcast....12-2009_all.htm
It's a little light on info but were adding more every day.


Nice work Motoxmann. I might have to try a 36mm PWK on my CR, the TMX has not given me too much problems, but I'd like to continue refining the old woods weapon.

  • hallsy

Posted December 25, 2009 - 10:03 AM

#17

The 99-01 kawasaki Kx125 have the short bodied 36pwk on them! I just bought one pretty cheap on ebay. They're identical to the 38pwk's that come on the 05 & newer Yz250's.Both have the TPS & Fuel cut silenoid. I cant wait to try it!!! :moon:

jimbo1143- have you installed the carb? What if anything did you have to do?
They might be identical in outer body dimensions but don't count on the rest being the same. 1 thing to note is the Kawasaki carbs usually come with a slightly different carb top. The difference being a permanantly attached longer cable holder that is curved and swivels. See part 16005 http://www.flatoutmo...=2000&fveh=8791
The longer retainer should require a different cable and might conflict with the frame? The kawasaki cable incorporates a clip that locks the sheath to the holder (nice feature) but will that cable work with a Honda throttle? Not trying discourage anyone. Just looking for any additional modifications that might be required for the conversion.

  • jimbo1143

Posted December 25, 2009 - 07:22 PM

#18

jimbo1143- have you installed the carb? What if anything did you have to do?
They might be identical in outer body dimensions but don't count on the rest being the same. 1 thing to note is the Kawasaki carbs usually come with a slightly different carb top. The difference being a permanantly attached longer cable holder that is curved and swivels. See part 16005 http://www.flatoutmo...=2000&fveh=8791
The longer retainer should require a different cable and might conflict with the frame? The kawasaki cable incorporates a clip that locks the sheath to the holder (nice feature) but will that cable work with a Honda throttle? Not trying discourage anyone. Just looking for any additional modifications that might be required for the conversion.


Haven't recieved the carb yet. I'm thinking that I'll probably switch the top from my 38pwk short body im currently using with the 36pwk or if all else fails then I can buy a used twist throttle from a 99-2000 kx125 off of ebay.:moon:

  • jimbo1143

Posted December 25, 2009 - 07:39 PM

#19

jimbo1143- have you installed the carb? What if anything did you have to do?
They might be identical in outer body dimensions but don't count on the rest being the same. 1 thing to note is the Kawasaki carbs usually come with a slightly different carb top. The difference being a permanantly attached longer cable holder that is curved and swivels. See part 16005 http://www.flatoutmo...=2000&fveh=8791
The longer retainer should require a different cable and might conflict with the frame? The kawasaki cable incorporates a clip that locks the sheath to the holder (nice feature) but will that cable work with a Honda throttle? Not trying discourage anyone. Just looking for any additional modifications that might be required for the conversion.


I been looking @ the diff between the two tops & the worst case senario would be to switch tops but I'll investigate that further once I have both carbs in my hands. I'll keep you informed as soon as I take a look @ both together.

  • hallsy

Posted December 25, 2009 - 08:32 PM

#20

I been looking @ the diff between the two tops & the worst case senario would be to switch tops but I'll investigate that further once I have both carbs in my hands. I'll keep you informed as soon as I take a look @ both together.


I didn't realize you had another carb that you could switch with, I'm guessing the tops will interchange. Let us know what you find out. :moon:





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