Author Topic: Keihin PWK38/40 slide cutaway measurements  (Read 436 times)

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Offline John Orchard

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Keihin PWK38/40 slide cutaway measurements
« on: May 27, 2019, 05:03:14 PM »
It took me a little while to compile the info, thought I'd share if anyone needs it. My carb is Chinese supplied and does not have any markings on the slides, hence the need for my homework  ;-)

I had a ping 'just' off closed throttle on my CR500, turned out to be slide cutaway.  In the PWK40 I am using, the carb came with a 7.0, it improved things going to a 6.0, then perfect with a 5.5.

Slide # -  Imperial  -  mm
5.5      -   .315"      -  8.000 (apparently PWK33 & 35)
6.0      -   .365       -  9.271
7.0      -   .385       -  9.779
8.0      -   .450       - 11.430
« Last Edit: June 09, 2019, 09:21:36 PM by John Orchard »
Johnny O - Tahition_Red factory rider.

Offline Hoony

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Re: Keihin PWK38/40 slide cutaway measurements
« Reply #1 on: May 27, 2019, 07:10:07 PM »
Hi John,

are you happy with the Bamboo Carb?

just wondering as if i ever get around to riding mine again i may consider the same.
Long time Honda Fan, but all bike nut in general, Big Bore 2 stroke fan.    http://www.youtube.com/watch?v=XJoKP6MawYI
1985 Honda CR500RF "Big Red"
1986 Honda CR250RG
2005 KTM 300EXC "The GruntMeister" ( I love that engine)

Offline John Orchard

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Re: Keihin PWK38/40 slide cutaway measurements
« Reply #2 on: May 28, 2019, 08:51:03 AM »
Al l was slow to get onto the PWK's, thinking "l can make the stock carb work ok", l did get the stock carb working ok, but l read so much on the internet that the PWK Airstriker (with air channel guides in intake bell) transforms the big CR's. l figured l'd give one a go once l saw them on ebay for only about $50, man it's only a block of alluminium that mixes fuel & air together, doesn't matter what country it was made in, l'll make it work.

The benefits of the flatslide really does make a difference over the stock aircooled round slide; she rips from the bottom-end so strong & quick (like the bike really needs that ?!!!!!).  Bigger buzz than any ride at a carnival ;-)

The PJ carb on the '85 CR, l read, to be a problem carb, like they say about the '84 round slide, any '85 l've ridden (125, 250 or 500) has always work well in my eyes.

Just get out and ride Al  ;-)
Johnny O - Tahition_Red factory rider.

Offline ralph311

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Re: Keihin PWK38/40 slide cutaway measurements
« Reply #3 on: May 28, 2019, 09:28:27 AM »
Where are you getting your slides from John?

FWIW I have a genuine pwk on my '84. I put it on to make it a little easier to start and was surprised at the extra grunt. Big difference.

Offline John Orchard

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Re: Keihin PWK38/40 slide cutaway measurements
« Reply #4 on: May 28, 2019, 09:48:01 AM »
Where are you getting your slides from John?

FWIW I have a genuine pwk on my '84. I put it on to make it a little easier to start and was surprised at the extra grunt. Big difference.


l contact the various suppliers of Chinese PWK rebuild kits on ebay, l get them to measure the slide cutaway before l order, they are happy to do that, they send me a pic with their verniers in place showing cutaway :-)
Johnny O - Tahition_Red factory rider.

Offline shoom

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Re: Keihin PWK38/40 slide cutaway measurements
« Reply #5 on: July 01, 2019, 05:28:29 AM »
Try the VM 36/4 with the powerjet.. supposedly you take 25% off of the main jet and the powerjet starts drawing from a spigot off the bowl when it comes on pipe and makes a hell of a difference. I've also see a guy put 'shutters' in the intake of a carb to good effect on a dt