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Discussion Starter #1
Anybody know the size of these carbs?

22/m
1980 Honda CB750
1972 Oldsmobile 442
 

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when you say size what do you mean? inlet size? or how big are the orifices to fit pods? How much CFM do they flow? or do you want to know something else (like rear spacing and od of the part that slips into the carb rubber)?

Don't you own a DOHC? Trying to ditch your CV carbs?
 

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Discussion Starter #3
Like their MM size, I heard their 24mm to 29mm and I was wondering what their throat size is.

Yea thats the plan, the carb spacing is close enough I should be able to make new manifolds to fit, I just want to make sure their big enough to breath with my engine

22/m
1980 Honda CB750
1972 Oldsmobile 442
 

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Keihin PD 28mm.
If you are looking for a set to put on the DOHC, the KZ 900 1000 carbs are closer in spacing.
DG
 

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Discussion Starter #5
Thanks. I was looking at them but they usually end at around 150-200 for a decent set, 100 for a set that needs a good rebuild. The SOHC CB750s I can find for like 20-50 for decent sets. 28mm should be fine for my bike since most people recommend 29mm for a street 750. I can change the spacing too and building new manifold shouldn't be too hard

22/m
1980 Honda CB750
1972 Oldsmobile 442
 

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77-79 GS 750 carbs are the same spacing as the kz carbs, they are 29mm mukuni VMs, and I just got a set of them off ebay for $20.
 

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Discussion Starter #7
thanks good to know, I'll start looking them up too

22/m
1980 Honda CB750
1972 Oldsmobile 442
 

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the 77-78 cb750F carbs are a good replacement carb for SOHC but I think they are too small for the DOHC bikes. Remember SOHC are 736ccs while DOHC are 749CC, and the SOHC has a massive head restriction cast into the design. As soon as you port a SOHC head the stock carbs start to look a little small, hence why people began fitting kz and GS carbs to their SOHC bikes.

The only advantage to the 77-78 carbs is that they have an accelerator pump, otherwise the other sohc carbs work just as well. The mukuni VM carbs are much better design than the kehins that came stock on the cb750s, plus it is way easier to get parts for them.

I betcha, that if you play with different year stock rubbers you can find a set that will adapt the GS carbs to the DOHC.
 

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wow
this geets guy has an answer for everything.
even gremlin hop-ups.
and yes mikunis do the fuel/air business better than anyone else.
-parks
 

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kin you imagine Geeto being around at a USCRA race weekend? he'd straighten us all out.
 

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Discussion Starter #14

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DG....

What were the GS850 carbs? I have a set of them around somewhere buried but I am not sure if they are the same as the 750s.

If what you are saying is true then you may have just made my day concerning the GS carbs on my workbench and the ones on my GS750, as they both have the hex nut float bowls. I also have a set of GS750L carbs that don't have the hex nut float bowls (the ones I won off ebay cheap) but I just assumed that was a difference with the L models since they had other parts different from the E models (like the airbox for example).
 

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The small bore Kawasaaki (KZ650/750) have the 3 horizontal ribs on the bodies. They came in 22mm and 24mm. The larger Kaws and Suzs don't have the 3 ribs on the carb bodies. These came in 26mm and 28. The early Kaw Z-1 900 carbs cam in 28mm and there were basically 2 versions. The early versions (72-73ish) had the large nut on the bottom (for eaasy jet changes). The later (73ish to 75)looked the same with out the nut on the bottom (no easy jet changes).

Top Row (Left to right)
1) VM 22 (22mm has the oval thing in the bell at 10 o'clock postion.
2) Early Z-1 28mm
3)26mm back side
Center Row
1) VM 24 (no oval thing at 10 O'clock) Accel Pump
2) Late Z-1 28mm
3) 28mm back side
Bottom Row
1) 28 Accel Pump carbs
2) 26mm Std Carbs
3) Late Z-1 Backside



Some of the early 29 smothbores came with Std looking float bowls (no nut for easy jet changes). Some 29's also came with accelerator pumps. All have the extra castings in the bell area.

Mikuni also made an accelerator pump that could be installed on the 29's. It installed where the extra casting is. Heres a set of late Z-1 carbs with them installed. The mounting area is alot thinner where the nozzles install, so they were mounted in a set of velocity stacks.



I dont know much about the GS 850's, but from what I gather, they came with 26mm Mikunis.
DG
 

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does anyone know if you can buy vm carb manifold adapters for a 1980cb750f?want the cv carbs gone. thanks Burt
 

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The Honda DOHC adaptors haven't been made in years(as far as I know). Most people usually get rid of the CV carbs and put some Keihin CRs or other aftermarket carbs on it. Thats the easiest and probably the best way to do it.The Keihin CRs have an adjustable spacing on them, where as the Mikuni VM's are set in 1 position and can't be easily modified.

The adaptors would look something like this(for mounting to the stock intake rubbers). I have never seen different rubber flanges for the DOHC to Mikuni VM KZ/GS spacing (probably due to the large port and (relativly) small diameter carb mount). SOHC to VM are easier to find.



The adaptors for the DOHC(like the style pictured) should have the inner holes and the outer diameters offset to get the spacing correct for the DOHC. They are a pain to get lined up correctly, but you only have to line them up 1 time.

DG
 

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Cycle exchange makes a conversion for the DOHC bikes to run dual VM mukunis (monster carbs too) but it is like $500. At that rate you might as well buy some Kehin CRs.

Dynoman.net sells the kits to adapt the VM GS suzuki carbs to the SOHC, I don't think they are the same rubbers as the DOHC but they might work. Unfortunatly at $100+ a set I am not about to buy them for expirement's sake.
 

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The SOHC VM adaptors wont work on the DOHC. The spigots in the SOHC head for the carbs are alot smaller than the DOHC spigots.
Keihin CR's are the way to go.
DG
 
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