Topic: Figuring Out My Carb

[Ellz10]

Quick question. I've tried looking up what type of carb I have and the size of it, but to no avail. I'm particularly interested in what the size of it is. Can I use a telescopic cylinder bore to figure it out or can I find everything I need to know out from the markings on the carb itself. If so, where would I look, because I've tried googling what I found and nothing popped up. Any help would be appreciated.

- Z

[goodtryer]

What year and what bike?

There will be some markings on the carbs. Usually on the sides just above the float bowl or on the top of the bracket that holds the 4 carbs together.

Typically something like PD41 or 42. Or 022, 069, 087. Might not have those exactly correct but you get the idea. You’ll recognize it when you see it.

[ekpent]

 Be nice if you could post a picture along with your bike info.

[newday777]

Quick question. I've tried looking up what type of carb I have and the size of it, but to no avail. I'm particularly interested in what the size of it is. Can I use a telescopic cylinder bore to figure it out or can I find everything I need to know out from the markings on the carb itself. If so, where would I look, because I've tried googling what I found and nothing popped up. Any help would be appreciated.

- Z

As a parts manager and you came in with that question and saying 'carb' and 'it' to me, that makes me think and ask you Z, are running a single carb and what bike?? Aftermarket carb or?
Not enough information from you doesn't get you answered until you fill in the gaps......

[robvangulik]

All his previous questions concerned what used to be a 750k7, so PD carbs should be right. But who knows what's left of it by now

[Ellz10]

What year and what bike?

There will be some markings on the carbs. Usually on the sides just above the float bowl or on the top of the bracket that holds the 4 carbs together.

Typically something like PD41 or 42. Or 022, 069, 087. Might not have those exactly correct but you get the idea. You’ll recognize it when you see it.

My apologies, I wasn't even thinking when I posted.

Bike is a 1977 Honda CB750K

I think it might be an aftermarket carb, but I'm not 100% sure.

Quick question. I've tried looking up what type of carb I have and the size of it, but to no avail. I'm particularly interested in what the size of it is. Can I use a telescopic cylinder bore to figure it out or can I find everything I need to know out from the markings on the carb itself. If so, where would I look, because I've tried googling what I found and nothing popped up. Any help would be appreciated.

- Z

As a parts manager and you came in with that question and saying 'carb' and 'it' to me, that makes me think and ask you Z, are running a single carb and what bike?? Aftermarket carb or?
Not enough information from you doesn't get you answered until you fill in the gaps......

[bryanj]

 ;)they aint original to that bike, there is a flat "pad" just above the brass vaccum takeoff plug in pic 2 on that will be some letters/numbers what are they and be precise

[Bankerdanny]

Those are 'round top' carbs from a 71-76 750K or 75-76 750F. Functionally those are all the same. The numbers stamped on the holder will tell you what year and model so you know what jet sizes and needle numbers they came with originally, but the jets and needles interchange.

[newday777]

Well your carbs are definitely Honda but not from a 1977. As Danny said 71-76....so are you sure you have a 77 and not a 76? What year model does the vin tag show on the steering neck?

Those carbs are 28mm
 
To help identify your bike.....
This is a 1976 K6 specs and picture.
https://bikez.com/motorcycles/honda_cb_750_f_1976.php

https://www.motorcyclespecs.co.za/model/Honda/honda_cb750k_76.html



1977 cb750 k7 specs and picture

https://www.autoevolution.com/moto/honda-cb-750-four-k7-1977.html

[Ellz10]

Those are 'round top' carbs from a 71-76 750K or 75-76 750F. Functionally those are all the same. The numbers stamped on the holder will tell you what year and model so you know what jet sizes and needle numbers they came with originally, but the jets and needles interchange.

That's what I was curious about. Good to know. The guy that did work on it back in '09 (last time it was on the road) said he bought it brand new. Now I'm doubting alot of things about him and what he did.

Well your carbs are definitely Honda but not from a 1977. As Danny said 71-76....so are you sure you have a 77 and not a 76? What year model does the vin tag show on the steering neck?

Those carbs are 28mm
 
To help identify your bike.....
This is a 1976 K6 specs and picture.
https://bikez.com/motorcycles/honda_cb_750_f_1976.php

https://www.motorcyclespecs.co.za/model/Honda/honda_cb750k_76.html



1977 cb750 k7 specs and picture

https://www.autoevolution.com/moto/honda-cb-750-four-k7-1977.html

100% sure it's a '77. The guy who worked on it last was a bit lackluster in a few departments.

I am glad to find out the size, for now I know I need to buy something else. I'm thinking a Mikuni 32mm or so if they make one for this bike.

Any suggestions on what to buy fellas? Obviously want to stick around 32 or so.

Bike is a '77 as mentioned.

Work that has been done is:

Carillo Connecting Rods
WiseCo Pistons 11.5 (836)
Super Studs (Cylinder Studs)
CX-11 Cam
New Cush Drive Bearing
Crankshaft Lightened and Balanced
Super Gasket Set (65mm)
Treated Main Bearings
Treated Rod Bearings
Adjustable Cam Sprocket Kit
Super Flow Valve Set
Cast Guides
Spring Set
Primary Chains
Tsubaki Cam Chains (Cryo)
Primary Chain Tensioner
Deluxe Bore & Hone .65 Over
Alternator Lightened and Balanced
Undercut Transmission
Cush Drive Rebuild
Combustion Chamber Blending Modification
Head Option #2 (Both sides of head surfaced, guides replaced and reamed, valve job)
Line Lap Engine Cases
Refurbish Electric Starter
Rebuild Output Shaft

[Ellz10]

I've seriously contemplated going with the Keihin CR31 setup. All around it seems as though it would serve me well in my setup. Thoughts?

[newday777]

I've seriously contemplated going with the Keihin CR31 setup. All around it seems as though it would serve me well in my setup. Thoughts?

There is a fair amount already posted on them.

http://forums.sohc4.net/index.php?topic=40413.0

[Ellz10]

I've seriously contemplated going with the Keihin CR31 setup. All around it seems as though it would serve me well in my setup. Thoughts?

There is a fair amount already posted on them.

http://forums.sohc4.net/index.php?topic=40413.0

I read that entire thread and now I'm conflicted as to whether or not to buy the CR29 or the CR31. I mean as I mentioned, the motor is modified so I'm not sure if it's modified ENOUGH to be able to run smoothly with the CR31.... thoughts?

[newday777]

I've seriously contemplated going with the Keihin CR31 setup. All around it seems as though it would serve me well in my setup. Thoughts?

There is a fair amount already posted on them.

http://forums.sohc4.net/index.php?topic=40413.0

I read that entire thread and now I'm conflicted as to whether or not to buy the CR29 or the CR31. I mean as I mentioned, the motor is modified so I'm not sure if it's modified ENOUGH to be able to run smoothly with the CR31.... thoughts?

I have not run either. I kept the stock 76 carbs on my 811(then later 836 bore), 3/4 race cam, 3 angle valve cuts and polished ports which did fine for my street riding and cross country runs back in the 70s.