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Author Topic: Mikuni RS interchangeability with CB750  (Read 1664 times)

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Offline redwillis1978

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Mikuni RS interchangeability with CB750
« on: January 09, 2016, 09:40:08 am »
Do any of the regular factory part numbers available for the Mikuni RS34 (GSXR 750 for example) swap over to the CB750K?


Offline dragracer

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Re: Mikuni RS interchangeability with CB750
« Reply #1 on: January 09, 2016, 10:42:22 am »
I don't think anyone but CycleEx sells RS carbs racked directly for an SOHC. The closest spacing i've found is an RS to fit either a GPZ900 or an FJ1100. Thats what i use on my dragbike.
http://www.cyclexchange.net/Rack%20of%204%20Carbs%20Page.htm

Offline Bill/BentON Racing

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Re: Mikuni RS interchangeability with CB750
« Reply #2 on: January 09, 2016, 12:32:46 pm »
They use the RS34-D21-K, they fit a GS750 and KZ750,GSX600 Katana,GSX-R 750 t9 start with, Bill
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Offline dragracer

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Re: Mikuni RS interchangeability with CB750
« Reply #3 on: January 09, 2016, 01:15:54 pm »
So Kenny is adjusting the spacing to fit the Honda's??

Offline redwillis1978

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Re: Mikuni RS interchangeability with CB750
« Reply #4 on: January 09, 2016, 01:32:57 pm »
Is it just adjusting the spacing? Enough "slack" in the stock setup?

Offline Bill/BentON Racing

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Re: Mikuni RS interchangeability with CB750
« Reply #5 on: January 09, 2016, 02:21:40 pm »
Not sure,was able to use std A&B cables. Here's a box pic. I'll ask Kenny next week.
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Over 35 years of experience working on vintage motorcycles, with a speciality in Honda SOHC/4 with a focus on the CB750 and other models as well from 1966 - 1985.
______________________________________
1993 HRC RS125 | 1984 NS400R | 1974 Honda CB750/836cc (Calendar Girl) | 1972 CB 500/550 Yoshi Kitted 590cc | 1965 Honda CB450 Black Bomber | 1972 Suzuki T350 | 1973 88cc | Z50/Falcons Pit Bike | 1967 CA100| 1974 CB350 (400F motor)...and more.
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Offline MessnerMoto

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Re: Mikuni RS interchangeability with CB750
« Reply #6 on: January 09, 2016, 02:35:30 pm »
Same single carbs... Different spacing... Logic of mass production ;)

Offline dragracer

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Re: Mikuni RS interchangeability with CB750
« Reply #7 on: January 09, 2016, 03:18:21 pm »
Gsxr spacing is not the same as the Honda spacing. My guess is due to the 34mm size that matches the needs of those smaller engines, that why the part number you listed was used versus the matched spacing. When I bought my carbs years ago, my research showed the fj1100 spacing was closest of any offered by in the rs line. Back then, they did offer them in 34mm but none were available when I got mine so I ended up purchasing the 36's. I had to offset grind the stock boots to make them work. Never looked back.

Offline MRieck

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Re: Mikuni RS interchangeability with CB750
« Reply #8 on: January 10, 2016, 05:55:18 am »
I have reracked a set of 34's for the 750. All the carbs have to be as close to centerline as possible. It takes some time but is not difficult.
Owner of the "Million Dollar CB"

Offline Bill/BentON Racing

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Re: Mikuni RS interchangeability with CB750
« Reply #9 on: January 10, 2016, 08:08:28 am »
Frank, they gotta be reracked. Thus is what Kenny starts with from Sudco.Hondas are different 80-100-80 if I recall correctly.
BentON Racing Website
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Over 35 years of experience working on vintage motorcycles, with a speciality in Honda SOHC/4 with a focus on the CB750 and other models as well from 1966 - 1985.
______________________________________
1993 HRC RS125 | 1984 NS400R | 1974 Honda CB750/836cc (Calendar Girl) | 1972 CB 500/550 Yoshi Kitted 590cc | 1965 Honda CB450 Black Bomber | 1972 Suzuki T350 | 1973 88cc | Z50/Falcons Pit Bike | 1967 CA100| 1974 CB350 (400F motor)...and more.
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Offline redwillis1978

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Re: Mikuni RS interchangeability with CB750
« Reply #10 on: January 10, 2016, 09:33:29 am »
But I start with the RS34-DK-21?

Online kmb69

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Re: Mikuni RS interchangeability with CB750
« Reply #11 on: January 10, 2016, 10:51:16 am »
Frank, they gotta be reracked. Thus is what Kenny starts with from Sudco.Hondas are different 80-100-80 if I recall correctly.

Stock CB750 Carbs: 77-80-77

« Last Edit: January 10, 2016, 10:54:00 am by kmb69 »

Offline PeWe

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Re: Mikuni RS interchangeability with CB750
« Reply #12 on: January 12, 2016, 03:47:15 am »
Mikuni TMR32-D7 for CB750 SOHC has 75-82-75 according to the catalogue

TDMR / TMR FLACHSCHIEBERVERGASER
KATALOG
WWW.MIKUNI-TOPHAM.DE
CB750 K6-76 1005cc JMR Billet block.
CB750 K2-75 stock looking project started 2017

Offline DingoLong87

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Re: Mikuni RS interchangeability with CB750
« Reply #13 on: September 11, 2018, 12:05:31 pm »
Hey guys, I hope reviving this post is alright but I've been researching and trying to find a new set of carbs for my 75 cb750 for a month or two now. Basically I narrowed my search down to Mikuni RS or Mikuni TMS. I've had a tough time finding something that I think will work. I only use my bike for casual riding and not for racing. I've ruled out the CRspecial carbs, stock CV carbs, awesome Yoshi TMR carbs and the Keihin FCR carbs just because I can't find them for my bike.

So... question is: are the RS the best for our CB750's? Is there a better alternative? The old CV's are pretty worn out and I'm looking for a pumper style carb to give me some more performance.

Any info you can provide would be greatly appreciated. Also, I'm a new member and I would have just posted a new topic but I couldn't figure out how. Can new members post topics?

Offline MessnerMoto

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Re: Mikuni RS interchangeability with CB750
« Reply #14 on: September 11, 2018, 12:36:52 pm »
the biggest down side of RS carbs is the "noise" when idling. The more overlap cam has the bigger the back pressure... and the flat slides are oscillating and making "noise". And flat slides in RS carb have a lot of space to oscillate...

By "noise" I mean like something is falling apart in the engine or like I am banging the engine with a hammer.

When I first started the engine I was thinking that something is ruined inside....

Offline scottly

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Re: Mikuni RS interchangeability with CB750
« Reply #15 on: September 11, 2018, 08:35:06 pm »
Hey guys, I hope reviving this post is alright but I've been researching and trying to find a new set of carbs for my 75 cb750 for a month or two now. Basically I narrowed my search down to Mikuni RS or Mikuni TMS. I've had a tough time finding something that I think will work. I only use my bike for casual riding and not for racing. I've ruled out the CRspecial carbs, stock CV carbs, awesome Yoshi TMR carbs and the Keihin FCR carbs just because I can't find them for my bike.

So... question is: are the RS the best for our CB750's? Is there a better alternative? The old CV's are pretty worn out and I'm looking for a pumper style carb to give me some more performance.

Any info you can provide would be greatly appreciated. Also, I'm a new member and I would have just posted a new topic but I couldn't figure out how. Can new members post topics?
Stock sohc 750 carbs are not CV carbs...
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 PeWe

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Re: Mikuni RS interchangeability with CB750
« Reply #16 on: September 18, 2018, 09:34:33 am »
Hey guys, I hope reviving this post is alright but I've been researching and trying to find a new set of carbs for my 75 cb750 for a month or two now. Basically I narrowed my search down to Mikuni RS or Mikuni TMS. I've had a tough time finding something that I think will work. I only use my bike for casual riding and not for racing. I've ruled out the CRspecial carbs, stock CV carbs, awesome Yoshi TMR carbs and the Keihin FCR carbs just because I can't find them for my bike.

So... question is: are the RS the best for our CB750's? Is there a better alternative? The old CV's are pretty worn out and I'm looking for a pumper style carb to give me some more performance.

Any info you can provide would be greatly appreciated. Also, I'm a new member and I would have just posted a new topic but I couldn't figure out how. Can new members post topics?
- What is done with engine?
My bike worked fine with stock CB750 K6 carbs, 836cc, ported head, cam.
If stock, install 836cc, ported head and cam before "better" carbs. Drain your wallet in correct order ;)

The Mikuni TMR 32 are much better, but engine can use them with more mods.
https://www.bikeside.de/shop/shop.php?bereich=Classic&aktion=anzeige_gross&ArtikelNr=59-2039
1500 euro + pods +200 Euro  rejet (135 mains,  32.5 pilots )since stock jetting has to be changed to fit pods if used. (needles set 2:6, stock 4:6 way too rich). It will cost around 1750 euro + shipping ??? ???
They are sold as prepared with velocity stacks too. (No pod adaptors)
CB750 stock throttle mechanism and cables works.
CB750 K6-76 1005cc JMR Billet block.
CB750 K2-75 stock looking project started 2017


Offline PeWe

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Re: Mikuni RS interchangeability with CB750
« Reply #18 on: September 20, 2018, 03:23:08 am »
I could not get the links to work.

I have bought main jets from UK for not that much. I have some in steps of 2.5 to my VM29. Work with TMR too.

https://www.ebay.co.uk/itm/EBC-Leerlaufd%C3%BCse-Miku-Gr32-5-Typ-N224-103-EBC224-32-5-0641702176206-Motorrad/331589358126?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

The last pilots from Germany also by chance since they might not be exactly equal to Mikuni. But they work fine.
https://www.ebay.co.uk/itm/271325913913?ViewItem=&item=271325913913&ssPageName=ADME:L:OC:GB:3160
CB750 K6-76 1005cc JMR Billet block.
CB750 K2-75 stock looking project started 2017

Offline Leino

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Re: Mikuni RS interchangeability with CB750
« Reply #19 on: September 20, 2018, 07:47:14 am »
the biggest down side of RS carbs is the "noise" when idling. The more overlap cam has the bigger the back pressure... and the flat slides are oscillating and making "noise". And flat slides in RS carb have a lot of space to oscillate...

By "noise" I mean like something is falling apart in the engine or like I am banging the engine with a hammer.

When I first started the engine I was thinking that something is ruined inside....
Lovely sound  ::)

Offline PeWe

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Re: Mikuni RS interchangeability with CB750
« Reply #20 on: September 20, 2018, 11:49:13 am »
the biggest down side of RS carbs is the "noise" when idling. The more overlap cam has the bigger the back pressure... and the flat slides are oscillating and making "noise". And flat slides in RS carb have a lot of space to oscillate...

By "noise" I mean like something is falling apart in the engine or like I am banging the engine with a hammer.

When I first started the engine I was thinking that something is ruined inside....
Lovely sound  ::)
Is it the chattering sound at idle? Flatslide throttles sounds like spanish castanets  ;D I was a little bit concerned fiirst but understood that the flatslides produced the sound and got the answer by googling flatslide + chatter

Nice whistling sound when twisting the throttle, almost like a turbo spool-up.
The idle sounds good when ignition and carbs are in sync.
CB750 K6-76 1005cc JMR Billet block.
CB750 K2-75 stock looking project started 2017

Offline Ilja

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Re: Mikuni RS interchangeability with CB750
« Reply #21 on: September 23, 2018, 05:21:07 am »
I have a rack of RS40 which I have for my gpz1100 engine but the spacing was just adjusted on the rails by the prev. owner.

Shouldnt be to hard with these carbs... :)

I think RS34 is perfect for the CB! Especially with the F2 heads... (34mm valves)

 

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