SubTexel

PWK conversion infomation

368 posts in this topic

Ok, seems more and more people are jumping onto the PWK conversion for their TMX equipped 01+ CRs.

So, lets start a thread with all the relevant information such as which PWKs from what model year bikes will swap right in without much of a hassle (correct length and all that jazz), wiring for TPS, and any other useful information. Would be nice if this made it as a sticky eventually but if not at least it'd be contained in one thread for easy reference. Reply and I will update the information below.

Lets start:

05-11 YZ250 PWK carbs (with TPS)

02-08 RM250 PWK carbs (with TPS)

??-07 KX250 PWK carbs (with TPS)

2000 CR250 PWK (no TPS)

TPS wiring information for those of use who wish to keep TPS (removing TPS causes the CPU to revert to a 2D map but causes no ill effects or performance degradation):

Keihin black=Mikuni green

Keihin yellow=Mikuni yellow/black

Keihin blue=Mikuni yellow/red

Carb lengths:

Older twist top PWK's = 91mm inlet to outlet.

TPS version of the PWK (top retained by 2 screws) = 75mm inlet to outlet.

01'- 03' CR 250 Mikuni's = 85mm inlet to outlet.

04'- 07' CR 250 Mikuni's = 75mm inlet to outlet.

Edited by SubTexel
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Ok, seems more and more people are jumping onto the PWK conversion for their TMX equipped 01+ CRs.

So, lets start a thread with all the relevant information such as which PWKs from what model year bikes will swap right in without much of a hassle (correct length and all that jazz), wiring for TPS, and any other useful information. Would be nice if this made it as a sticky eventually but if not at least it'd be contained in one thread for easy reference. Reply and I will update the information below.

Lets start:

05-11 YZ250 PWK carbs (with TPS, long style carb)

02-08 RM250 PWK carbs (with TPS, long style carb)

??-07 KX250 PWK carbs (with TPS, ?? style carb)

2000 CR250 PWK (no TPS, short style carb)

TPS wiring information for those of use who wish to keep TPS (removing TPS causes the CPU to revert to a 2D map but causes no ill effects or performance degradation):

Keihin black=Mikuni green

Keihin yellow=Mikuni yellow/black

Keihin blue=Mikuni yellow/red

Awesome, Thanks!!!!!!!!

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I'm confused, or maybe I don't understand what you mean by long and short carbs. The overall length (inlet to outlet) of the TPS equipped PWK's is shorter than the older twist top version (00' CR 250).

Older twist top PWK's = 91mm inlet to outlet.

TPS version of the PWK (top retained by 2 screws) = 75mm inlet to outlet.

01'- 03' CR 250 Mikuni's = 85mm inlet to outlet.

04'- 07' CR 250 Mikuni's = 75mm inlet to outlet.

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I'm confused, or maybe I don't understand what you mean by long and short carbs. The overall length (inlet to outlet) of the TPS equipped PWK's is shorter than the older twist top version (00' CR 250).

Older twist top PWK's = 91mm inlet to outlet

TPS version of the PWK (top retained by 2 screws) = 75mm inlet to outlet

01'- 03' CR 250 mikuni's = 85mm inlet to outlet

04' -07' CR 250 mikuni's = 75mm inlet to outlet

Mistake on my end... Reason this thread exists to get that information out there. That is good information to add :thumbsup: There are shorter style PWKs (with TPS) however... Found on some of the KTMs and older RM/KX models.

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Mistake on my end... Reason this thread exists to get that information out there. That is good information to add :thumbsup: There are shorter style PWKs (with TPS) however... Found on some of the KTMs and older RM/KX models.

More confusion??? As far as I know all the PWK bodies from 36mm through 39mm diameter bores, that are made to accept a throttle position sensor (TPS), are of the same length. They will be 75mm inlet to outlet. Some of them don't actually contain a TPS but use the same body, such is the case with the newer KTM's, most of which are 36mm but they used some 38mm's on certain models. I have a 99' KX-250 TPS PWK, and a 06' KTM 250 SX PWK which is the TPS body but doesn't actually contain a TPS. They both measure 75mm inlet to outlet, which is the same as my 03 YZ 250 TPS PWK.

Edited by hallsy

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More confusion??? As far as I know all the PWK bodies from 36mm through 39mm that are made to accept a throttle position sensor (TPS), are of the same length. They will be 75mm inlet to outlet. Some of them don't actually contain a TPS but use the same body, such is the case with the newer KTM's, most of which are 36mm but they used some 38mm's on certain models. I have a 99' KX-250 TPS PWK, and a 06' KTM 250 SX PWK which is the TPS body but doesn't actually contain a TPS. They both measure 75mm inlet to outlet, which is the same as my 03 YZ 250 TPS PWK.

Ok, good info. I've had people in the past on this and other forums swear only certain TPS carbs would work because of length, however it seems to be some miscommunication / misunderstanding.

But either way, any other info that could be added to this thread would be great.

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Ok, good info. I've had people in the past on this and other forums swear only certain TPS carbs would work because of length, however it seems to be some miscommunication / misunderstanding.

But either way, any other info that could be added to this thread would be great.

Well anything is possible but again I think they all use the same body. Certainly there will/can be differences between the carbs internally.

Here's a list I compiled of the PWK's used by the manufacturer's for the 250. I can't say it's 100% correct but should be close enough to provide a broader base to choose from. In any case it's buyer beware! I have seen many carbs misrepresented on that auction site. So just because a carb has a twist top doesn't automatically mean it's a PWK, nor does the sellers claim of a specific carb make it so.

CR-250

99'-00'=twist top PWK

KX-250

88'-97'=twist top PWK

98=twist top PWK with powerjet

99'-07=TPS PWK

RM-250

97'=twist top PWK

98'-99'=twist top PWK with powerjet

00'= twist top PWK with powerjet and adjustable choke

01'-02'=TPS PWK with adjustable choke

03'-08'=TPS PWK

YZ-250

00'-11'=TPS PWK

I don't know what size those carb bores are or which ones are air strikers and which ones are standard PWK's.

In this pic from left to right is the..

99' CR-250 twist top PWK

99' KX-250 TPS PWK

06' SX 250 TPS PWK body but isn't drilled/tapped for either the TPS or the Powerjet

01' CR-250 Mikuni

013-2.jpg

Notice that the KX carb has a different cable holder (longer). This one is affixed to the carb top via a flare which allows it to swivel but it can't be removed (unscrewed) from the top. This carb would most likely require the use of the KX throttle and throttle cable or switching to another top.

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I remember reading that Jeremy Mcgrath used a spiecal short carb. I don't remember whitch bike but seems like it was when he was racing Yanaha, the outlet of the carb was shorter than stock for more top end.

Also i talked to Carb Parts Warehouse one time when i was considering putting a small bore carb on a 2002 cr250 for more bottom. I noticed in the Dimensions that the 36mm carb had the same bore as the 38 or 39mm. what ever was stock. I ask them about it and they said that the 36mm had the same bore but the jeting was different and the only way i could get one with a 36mm bore was to get one that came stock on a ktm or other bike that had a 36mm stock carb.

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I remember reading that Jeremy Mcgrath used a spiecal short carb. I don't remember whitch bike but seems like it was when he was racing Yanaha, the outlet of the carb was shorter than stock for more top end.

It's possible that the factory teams could have used special carbs. However about the time that Mc went to Yamaha, they were using the Keihin PWM (96'-99') on the YZ 250. This carb did have a shorter overall length compared to the screw top PWK's of the time, and is touted by Keihin as having a "shorter overall length for better top end power". However that overall length is 75mm, the same as the TPS PWK. Yamaha switched from the PWM to the TPS PWK in 00'.

Also i talked to Carb Parts Warehouse one time when i was considering putting a small bore carb on a 2002 cr250 for more bottom. I noticed in the Dimensions that the 36mm carb had the same bore as the 38 or 39mm. what ever was stock. I ask them about it and they said that the 36mm had the same bore but the jeting was different and the only way i could get one with a 36mm bore was to get one that came stock on a ktm or other bike that had a 36mm stock carb.

Which PWK are you referring to here, the twist top or the TPS? They should be able to provide you with a 36mm twist top. For clarity the bore of the carb is the size of the hole through the center. A 36mm bore is smaller than a 39mm, but Keihin does use the same body to produce both carbs, so then the outside dimensions of the 36mm are the same as the 39mm.

Carbparts Warehouse or any other Keihin dealer can only provide us with the carbs that Keihin offers to the aftermarket. The TPS PWK is not one of them. So if it was the TPS PWK that you were looking for in a 36mm bore, then yes you'd have to get it from an O.E.M.

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I am quite interested in this swap even though I have the JD kit for the stock 02 carb. Do the twist off PWKs us the same throttle cable as the mikuni?

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i went back and looked at the drawing, you are right it is the same od on the twist off. But i don't understand why cpw told me the size was the same when they new i was looking for a smaller bore carb for more bottom end. Anyway that was years ago so i don't need it anymore. The carb that Mcgrath uses in the picture it showed the outlet going to the intake was so short that the boot would just fit on, i remember it saying that it was a spiecal shorten carb for more top end. Thanks for the info.

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I am quite interested in this swap even though I have the JD kit for the stock 02 carb. Do the twist off PWKs us the same throttle cable as the mikuni?

Yup, I'm using my stock '02 cable with the PWK.

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This is sweet...I remember i did this swap on my 01 cr when i had it.

does the 07 yz carb w/ the tps directly plug into the 02-07 cr's ?

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The longer body, screw top, non-TPS 38mm PWK Air Stryker carbs are also used on older KTM 2-strokes (200, 250, & 300 - started in 2002). The KTM description in the OEM part catalog is "PWK 38AG". I am using a 2002 KTM 200 EXC carb on my 2002 CR250R with 40 pilot, 168 main, 7.0 slide, and red James Dean needle at SL. Picked it up for about $65 on Ebay. The slide on a 200 EXC not a 7.0 (preferred cut), but can be machined to a 7.0 by RB Designs for about $20 (includes shipping). The PWK AS carb is the best $$$ that I have spent on an upgrade besides a Boysen Rad valve, FMF Gnarly pipe (gives it 4-stroke style power output), and MX Bonz Airbox kit.

Hope this helps!

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I have a stock 06 cr with fmf pipe and silencer with a rad valve, just put the carb on and fired it for the first time, crisp as can be. I started with 2000 slide, needle, and the reccomended jets, and I wish I did the swap when I first heard about it!! Great info here, thanks, but I have one small question with the wiring colors. MY cr wires are green, yellow with red, and yellow with blue, not black, and the kx tps has black with green stripe, white with black, and red with a green stripe. I'd like to rig this up, but this sunday, I'm taking it out to cadillac ranch and rying it out, tps or not, it sounds that good on startup and during a warmup!! As for the cap, the only place I could find a part number was with KTM, thanks, and got one from Powersports warehouse ktm. Thanks in advance for all that have made this thread so usefull!

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I am also wondering how to hook this up. I am currently deployed so it is going to be a little bit before I can get home and hook every thing up. But I also have a 06 CR250 and I just ordered a 06 YZ 250 carb off Ebay. So when I get home I should be able to switch it out and the TPS should hook right up correct? Also do you think I should leave the jets in the PWK the same?

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HI, I just goyt back and I noticed that they are two sets of wires coming out a a 06 YZ 250 Carb. I also have a 06 CR 250

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