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Author Topic: Honda RCB  (Read 712 times)

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Offline Wezzo

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Honda RCB
« on: September 22, 2025, 01:36:18 AM »
Hi, could anyone point me at some documents, urls, etc that outline what Honda did to the SOHC engine to bring it to RCB spec. Anyone done one?
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Offline newday777

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Re: Honda RCB
« Reply #1 on: September 22, 2025, 02:10:14 AM »
Quote from: Wezzo on September 22, 2025, 01:36:18 AM
Hi, could anyone point me at some documents, urls, etc that outline what Honda did to the SOHC engine to bring it to RCB spec. Anyone done one?
What is this RCB spec?
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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 newday777

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Re: Honda RCB
« Reply #2 on: September 22, 2025, 02:28:30 AM »
Have contacted Robinson Precision Engines (RPE) in Australia?

http://forums.sohc4.net/index.php/topic,153905.msg1759725.html#msg1759725
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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

Online seanbarney41

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Re: Honda RCB
« Reply #3 on: September 22, 2025, 07:10:47 AM »
I don't think Newday knows about the Honda RCB endurance racer efforts...so yeah, RPE ebgines are, of course cool, but not what you asked about?  I believe if you search, there are some threads here about the history of the RCB.  I have read some, but am no expert.  I believe they ultimately developed a dohc head for the old sohc bottom end and it finally ended being the basis for the dohc production engine.
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If it works good, it looks good...

Offline newday777

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Re: Honda RCB
« Reply #4 on: September 22, 2025, 08:30:11 AM »
I didn't find any information doing a search and no i wasn't aware of them.
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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 scottly

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Re: Honda RCB
« Reply #5 on: September 22, 2025, 08:40:33 AM »
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Don't fix it if it ain't broke!
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Offline MRieck

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Re: Honda RCB
« Reply #6 on: September 22, 2025, 09:48:30 AM »
The article didn't mention the RCB's had gear primary drives.
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Online seanbarney41

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Re: Honda RCB
« Reply #7 on: September 22, 2025, 10:13:28 AM »
Well, I believe there were threads here but I could not turn them up either...plenty to read from a google search though.
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If it works good, it looks good...

Offline newday777

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Re: Honda RCB
« Reply #8 on: September 22, 2025, 10:35:09 AM »
Interesting.
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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 01Thomas

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Re: Honda RCB
« Reply #9 on: September 22, 2025, 11:15:53 AM »
Hi
I do have magazine articles of the Honda RCB but I'll have to dig them out and scan them. In the meanwhile I have these two photos on my hard-drive.
cheers, Thomas
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1971 Honda CB750 Four K1 [Engine: CB750E-1113521 / Frame: CB750-1113838]
1977 Seeley Honda CB750F (F1) [Engine: CB750E-2551214 / Frame No: SH7-655F]

'96 Yamaha YZF750SP & '81 Moto Guzzi SP1000 & '80 Moto Guzzi 850 LeMans II & '82 Bimota KB-3 [Frame No 49] & '66 Ducati 50 SL/1 & '53 Miele K-50 & '38 Miele 98

Offline simon#42

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Re: Honda RCB
« Reply #10 on: September 22, 2025, 11:34:48 AM »
this is a nice one . took this photo in july
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Offline 01Thomas

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Re: Honda RCB
« Reply #11 on: September 22, 2025, 12:18:09 PM »
When was the RCB Honda current? I'm thinking 1977 ? Knowing this will help me with where to look in my pile of magazines.
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1971 Honda CB750 Four K1 [Engine: CB750E-1113521 / Frame: CB750-1113838]
1977 Seeley Honda CB750F (F1) [Engine: CB750E-2551214 / Frame No: SH7-655F]

'96 Yamaha YZF750SP & '81 Moto Guzzi SP1000 & '80 Moto Guzzi 850 LeMans II & '82 Bimota KB-3 [Frame No 49] & '66 Ducati 50 SL/1 & '53 Miele K-50 & '38 Miele 98

Offline scottly

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Re: Honda RCB
« Reply #12 on: September 22, 2025, 12:24:58 PM »
1976 through 1980 according to the page I posted.
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Don't fix it if it ain't broke!
Helmets save brains. Always wear one and ride like everyone is trying to kill you....

Offline 01Thomas

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Re: Honda RCB
« Reply #13 on: September 22, 2025, 12:46:06 PM »
Thanks Scottly
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1971 Honda CB750 Four K1 [Engine: CB750E-1113521 / Frame: CB750-1113838]
1977 Seeley Honda CB750F (F1) [Engine: CB750E-2551214 / Frame No: SH7-655F]

'96 Yamaha YZF750SP & '81 Moto Guzzi SP1000 & '80 Moto Guzzi 850 LeMans II & '82 Bimota KB-3 [Frame No 49] & '66 Ducati 50 SL/1 & '53 Miele K-50 & '38 Miele 98

Offline Tim2005

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Re: Honda RCB
« Reply #14 on: September 23, 2025, 12:12:02 PM »
The best RCB info I have seen is on this Facebook page, https://www.facebook.com/TeamRCBCaillouBedier  , they have an RCB that they have rebuilt over the years. They have done amazing work, even casting a new cylinder head, and from what I have seen the motor has little in common with the CB750 sohc engine
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Offline MRieck

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Re: Honda RCB
« Reply #15 on: September 24, 2025, 11:21:46 AM »
This article has good pics of the engine internals. You can definitely see the SOHC heritage.
https://www.vf750fd.com/Joep_Kortekaas/honda_endurance_history.html
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Offline MRieck

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Re: Honda RCB
« Reply #16 on: September 24, 2025, 11:47:34 AM »
Interesting that Honda want back to a chain primary in 1980....seems like a step backwards but maybe it was done to make the drive lighter....I don't think they were concerned about extra maintenance. Also interesting are the 4 cams using Oldham couplers ala CBX and early 166 250. I don't think the old 500cc GP engines used the cam couplers but I could be wrong.
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Offline turboguzzi

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Re: Honda RCB
« Reply #17 on: September 25, 2025, 02:04:59 PM »
some more details here + a video of Okada taking it for a spin :)

https://honda.racing/features/rcb1000
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Offline Wezzo

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Re: Honda RCB
« Reply #18 on: October 03, 2025, 11:23:37 PM »
Thank you everyone. Some interesting reading
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