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Author Topic: 29mm Keihin Special tuning  (Read 825 times)

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Offline rokhedjo

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29mm Keihin Special tuning
« on: December 11, 2023, 09:16:35 AM »
Has anyone put the Keihin 29 Specials on their bike? Need some advice on tuning. Initial out of box not good, seems to need needles raised, different jetting? They came with 120 mains
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Offline rokhedjo

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Re: 29mm Keihin Special tuning
« Reply #1 on: December 11, 2023, 09:18:20 AM »
Also, ported head, oversize Kibblewhite 5mm valves, mild cam, Dyna ignition, and 4 into one exhaust.
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Offline newday777

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Re: 29mm Keihin Special tuning
« Reply #2 on: December 11, 2023, 10:35:16 AM »
rokhedjo

When you ask for help please include what the bike is you are working on.
As to tuning, you will have to add more information as to what motor size specifics/ build you have
« Last Edit: December 12, 2023, 02:49:21 AM by newday777 »
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Stu
Honda Parts manager in the mid 1970s Nashua Honda
My current rides
1975 K5 Planet Blue my summer ride, it was a friend's bike I worked with at the Honda shop in 76, lots of fun to be on it again
1976 K6 Anteres Red rebuilding project, was originally my brother's that I set up from the crate, it'll breath again soon!
Project 750s, 2 K4, 2 K6, 1 K8
2008 GL1800 my daily ride and cross country runner

Prior bikes....
1972 Suzuki GT380 I had charge of it for a year in 1973 while my friend was deployed and learned to love street riding....
New CB450 K7 after my friend returned...
New CB750 K5 Planet Blue, demise by ex cousin in law at 9,000 miles...
New CB750 K6 Anteres Red, to replace the totaled K5, I sold this K6 at 45k in 1983, I had heavily modified it, many great memories on it and have missed it greatly.....
1983 GL1100A, 1999 GL1500 SE, 1999 GL1500A

Offline Jerry Rxman Griffin aka MuthaF'er

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Re: 29mm Keihin Special tuning
« Reply #3 on: December 11, 2023, 10:59:36 AM »
Elevation also

You can start with mains but remember that needles overlap mains and mains are mainly for WOT. With these carbs the needles are VERY easy to adjust.

I was surprised at how much smaller mains needed to be than anticipated on my 915 with stage 4 JMR head at 6900' with CR31's.

Please advise the symptoms at different rpms. IMO start with needles since that's what you'll be using most of the time.
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As of today 3/13/2012 my original owner 75 CB750F has made it through 3 wives, er EX-wives. Free at last.  ;-)

Offline johno

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Re: 29mm Keihin Special tuning
« Reply #4 on: December 11, 2023, 10:15:47 PM »
Sorry to but in on the thread but Jerry you need to take your bad girl to the 1 mile airstrip somewhere in the states, no salt no dirt just show that #$%* who's the boss .......... and tell us how fast she goes  :D 8)
cheers Johno
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Offline paul_cb836

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Re: 29mm Keihin Special tuning
« Reply #5 on: December 12, 2023, 12:17:51 AM »
I have CR29s on my 836 (ported head, 315 cam). Not really had any problem at all tuning. I would have to check but pretty sure I am running much smaller mains than 120.
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Offline newday777

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Re: 29mm Keihin Special tuning
« Reply #6 on: December 12, 2023, 02:46:57 AM »
Quote from: rokhedjo on December 11, 2023, 09:16:35 AM
Has anyone put the Keihin 29 Specials on their bike? Need some advice on tuning. Initial out of box not good, seems to need needles raised, different jetting? They came with 120 mains
Are you watching this thread of yours?? No reply yet from you.....
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Stu
Honda Parts manager in the mid 1970s Nashua Honda
My current rides
1975 K5 Planet Blue my summer ride, it was a friend's bike I worked with at the Honda shop in 76, lots of fun to be on it again
1976 K6 Anteres Red rebuilding project, was originally my brother's that I set up from the crate, it'll breath again soon!
Project 750s, 2 K4, 2 K6, 1 K8
2008 GL1800 my daily ride and cross country runner

Prior bikes....
1972 Suzuki GT380 I had charge of it for a year in 1973 while my friend was deployed and learned to love street riding....
New CB450 K7 after my friend returned...
New CB750 K5 Planet Blue, demise by ex cousin in law at 9,000 miles...
New CB750 K6 Anteres Red, to replace the totaled K5, I sold this K6 at 45k in 1983, I had heavily modified it, many great memories on it and have missed it greatly.....
1983 GL1100A, 1999 GL1500 SE, 1999 GL1500A

Offline Jerry Rxman Griffin aka MuthaF'er

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Re: 29mm Keihin Special tuning
« Reply #7 on: December 12, 2023, 12:13:52 PM »
Quote from: johno on December 11, 2023, 10:15:47 PM
Sorry to but in on the thread but Jerry you need to take your bad girl to the 1 mile airstrip somewhere in the states, no salt no dirt just show that #$%* who's the boss .......... and tell us how fast she goes  :D 8)
cheers Johno

LMAO Johno. I agree
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As of today 3/13/2012 my original owner 75 CB750F has made it through 3 wives, er EX-wives. Free at last.  ;-)

Offline Tracksnblades1

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Re: 29mm Keihin Special tuning
« Reply #8 on: December 12, 2023, 03:28:52 PM »
Quote from: paul_cb836 on December 12, 2023, 12:17:51 AM
I have CR29s on my 836 (ported head, 315 cam). Not really had any problem at all tuning. I would have to check but pretty sure I am running much smaller mains than 120.

Not uncommon back in the day…

836s can provide a strong signal on OEM carbs..

Especially with a short cam…
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Offline rokhedjo

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Re: 29mm Keihin Special tuning
« Reply #9 on: December 19, 2023, 08:42:34 AM »
Sorry, 1972 CB750k. 812cc yoshimura pistons, web cam SX 10
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Offline Old Scrambler

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Re: 29mm Keihin Special tuning
« Reply #10 on: December 20, 2023, 10:53:34 AM »
Assuming your tuning for the street................If your near sea-level with 120s, try lowering the needles. If higher elevation, get smaller mains and play with needle settings. Ultra-fine tuning deals with needle-taper. Smooth transition from idle may involve air-mixture.
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Offline rokhedjo

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Re: 29mm Keihin Special tuning
« Reply #11 on: December 21, 2023, 04:40:09 PM »
Thanks
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