Topic: 1969 CB 750 Carbs

[Hondell]

Hi All:

I've got a set of '69 carbs sitting around. Any performance advantage over a set of '72 carbs?

Thanks

[puppytrax]

Wow...An actual Sandcast carb set??   

I gotta believe someone on eBay will pay 3 - 4 hundred for them...   

[GroovieGhoulie]

The big difference was the jetting.  Hondaman talked about the year differences in one of his posts.

The K0 has 120 main jets while the K2 had 100 mains.  If you live at sea level and have stacks or pods, you may want the fatter jets.  If you live at altitude, you want the smaller jets.  Japan is very near sea-level and Honda engineers overjetted so they would run acceptably at sea-level.  The jetting is too fat as the altitude rises.

The K2 carbs have the advantage of the linkage to lift all the slides.  Makes synchronizing a snap and lets them stay in tune better.  The 4-cable arrangement was a cost-saving measure by Honda (the prototype bikes had linkages) and the #4 carb would always lose sync first because it's cable was the shortest and would stretch the most quickly.

I would use the K2 carbs with the fatter K0 jets specs if I was looking at a basis to start for a performance bike.

[Bob Wessner]

and the #4 carb would always lose sync first because it's cable was the shortest and would stretch the most quickly

Mine are in pairs and both cables in each set of two are the same length. The two outer carbs (#1 & #4) are the longest because they are the farthest from the mid-line with #2 and #3 the shortest.

[GroovieGhoulie]

Hmm.. I reacll someone posting that because of the design, the carb nearest the petcock, #4 I believe, would have the shortest cable and it would stretch first, causing an imbalance.  If I'm out to lunch on this one, glad thigns were set straight.  Don't have a K0 (yet), and when I do , I'm sure I'll learn ALL ABOUT the "fun" that is the K0 carb setup.

[Bob Wessner]

Mind you, I never measured them, but this is from a "view recollection." Next time the tank and carb tops are off, I will measure them. Who knows, maybe I have them mis-matched.. but it runs fine.. so far. 

[HondaMan]

and the #4 carb would always lose sync first because it's cable was the shortest and would stretch the most quickly

Mine are in pairs and both cables in each set of two are the same length. The two outer carbs (#1 & #4) are the longest because they are the farthest from the mid-line with #2 and #3 the shortest.

Bob, you have the "retrofit" cables, then.
The first K0 cables were 4 different lengths, coming out of one "splitter". The one on #4 was only about 5" long from the splitter, and it would often get pulled up out of the little socket on top, causing that cylinder to go into "high idle" unexpectedly, after unlocking the parked handlebars (turned left and locked). First, Honda issued a 6" long piece, and we'd have to disassemble the whole #$%@! thing and install the little 6" cable, then re-sync the whole set.    Then, they came out with the "retrofit cable set", like you have. Those were better, stretched less, too.

[techy5025]

I have two sets of K0 carbs sitting on the shelf. If you look at
the pains that Honda went to on the later carbs to eliminate
slack and tie all four carbs together, you will understand why
I gave up on them.

Jim

[Bob Wessner]

and the #4 carb would always lose sync first because it's cable was the shortest and would stretch the most quickly

Mine are in pairs and both cables in each set of two are the same length. The two outer carbs (#1 & #4) are the longest because they are the farthest from the mid-line with #2 and #3 the shortest.

Bob, you have the "retrofit" cables, then.
The first K0 cables were 4 different lengths, coming out of one "splitter". The one on #4 was only about 5" long from the splitter, and it would often get pulled up out of the little socket on top, causing that cylinder to go into "high idle" unexpectedly, after unlocking the parked handlebars (turned left and locked). First, Honda issued a 6" long piece, and we'd have to disassemble the whole #$%@! thing and install the little 6" cable, then re-sync the whole set.    Then, they came out with the "retrofit cable set", like you have. Those were better, stretched less, too.

Thanks, that certainly explains what I see versus others. Who'd a thunk . Sure glad we have you to explain some of these nuances.

[toycollector10]

I just give up, I'm not going near those bloody things while my K0 is running ok....