1969 CB750 carbs

[Lucky 1]

I was very excited today because I got a set of (1969 EDIT) Honda CB750 carbs!!!

They are the best Honda ever made as far as I am concerned.
No throttle shafts,no lifting arms .

Just a simple cable to pull up the slides.
Clips on the float bowls. All adjustments easy to get to.
I am really happy to get them.

I do need a base mounting plate for them though.

[seestheday]

Sweet.  Congrats man.

Pics?

[shinyribs]

I was wondering about the four individual cables. How do they connect to the one throttle cable? I've never seen that.

[Re-run]

You might think they are sweet, wait till you actually adjust them. The 4 cables make it very hard to sync.
As for actual performance, they are no better than anything else, just more labor intensive.
Difficulties in adjustment are why honda ditched them after a year and went to the lifter style used till 76.
Sure they might be simple for everything else but I knew a number of guys with 69s and they hated syncing these carbs and how often it had to be done.

But hey, if you like them, knock yourself out. Just don't expect a 5ph jump

[rrgunslinger]

Take a look at this.   There is a disk in the round chamber that the single pull cable runs to in the middle. Then four holes that the other cables that go to the carbs run to four holes along the edge or the same disk.  The cable in the middle pulls all four of the carb cables at the same time. 

http://www.bikebandit.com/houseofmotorcycles/1969-honda-cb750k0/o/m9141#sch394977

 

On Thu, Jun 7, 2012 at 11:35 PM, shinyribs [via Honda CB750'S] <[hidden email]> wrote:

I was wondering about the four individual cables. How do they connect to the one throttle cable? I've never seen that.

Montvale,Virginia
 Piute said it best:  "wheres my 10mm?"
Hellbilly-"that is a great way to tell if you have come to your senses, when you start drilling random holes in things... "

LukeM-"Scooters rock, especially when they're in posse formation. "

Those who are too smart to engage in politics are punished by being governed by those who are dumber. ~Plato

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[Lucky 1]

This is a photo of the 1 into 4 mechanism.
Very simple and very effective.

Matter of fact there are many used ones for sale on Ebay still in working condition.

[Lucky 1]

I was a dealership mechanic during that time.

No problems.
Matter of fact it was the shop mechanics back then that developed sync
gauges to use on multi cylinder motorcycles.

When you wanted to change needle clip position for 4 into one exhausts it made the job VERY easy.
Did not even have to take the carbs off of the bike.

All you did was unscrew the carb top, pull the spring back and unhook the cable through the
slit in the side of the carb, make your clip change and reinstall.

[shinyribs]

I'm still curious as to where the 1 into 4 mechanism is located on the bike. Does it just hang in-line with the cable from the throttle to the 4 carb cables? Just kinda floating?

[rrgunslinger]

under the tank

On Fri, Jun 8, 2012 at 5:36 PM, shinyribs [via Honda CB750'S] <[hidden email]> wrote:

I'm still curious as to where the 1 into 4 mechanism is located on the bike. Does it just hang in-line with the cable from the throttle to the 4 carb cables? Just kinda floating?

Montvale,Virginia
 Piute said it best:  "wheres my 10mm?"
Hellbilly-"that is a great way to tell if you have come to your senses, when you start drilling random holes in things... "

LukeM-"Scooters rock, especially when they're in posse formation. "

Those who are too smart to engage in politics are punished by being governed by those who are dumber. ~Plato

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[Piute]

          To eacxh there own , many still prefer drum brakes,points,spokes,
                 Make your bike your own and have fun doing and riding,

[shinyribs]

I love drum brakes and spokes!...too lazy for points. I wish I had a drum for the front of the Water Buffalo

[Piute]

shinyribs wrote

I love drum brakes and spokes!...too lazy for points. I wish I had a drum for the front of the Water Buffalo

                                 Café

[Re-run]

I was just saying what a number of people told me about these carbs and sync difficulties.
Performance isn't any better or worse than the other carbs, they just actuate differently. It was a method honda changed after a year.

[Lucky 1]

The 4 into 1 cable tube enclosure is between the throttle and the carbs.
It is just zip tied loosely near the fame like other throttle cable housings would be .

[Lucky 1]

Yes....

[Lucky 1]

The carbs were the same from 1969 - 1970

The 1969 CB750s had more power than all the other CB750's that were stock.
They had about 65 HP and the 1978 had about 50 HP. Many factors that detuned the later models.

It is partly the cam and the pistons and jetting of the carbs.
Also the type of exhaust system and intake system caused  loss of power.

[Re-run]

Actually the f2 beats the 69, even the 77k beats the 69 in the quarter. Hard to see that with more weight if it had less power.
"The K-model is all this plus another 3 percent. It has an edge because it’s built and sold as a touring bike, so factors such as ground clearance and weight aren’t as significant as they are to a bike with “Super Sport” in its name. Ideally the K model would also have ComStar wheels, dual horns, a rear disc and the F’s power, but even without them, it’s a fine touring machine tainted only by less than satisfactory suspension compliance. Its 1/4-mile time of 13.33 doesn’t seem impressive compared to the F’s hot-blooded 12.7, until you realize it’s still three tenths quicker than the original CB750, three tenths quicker than the current Yamaha 750, and quicker than the BMW 750. In short it’s no slouch, and there’s a simple explanation why: the K engine is last year’s Super Sport engine with the new accelerator-pump carburetion system."
http://www.sohc4.net/index.php/hondacb750f2cb750k7-cyclefeature-1977/  Here is the cycle mag article.
The F3/k8 are virtually identical to the 77 year.

I am glad you like your carbs. More power to you but the results just don't add up.
HP readings also changed in how they were measured. In 69 it was measured at the crank.
Later it was measured at the wheel. The true wimpiest year was 74. Honda really butched the hp that year. Incidentally, that was the year of 18 tooth front sprockets. 

You should be happy about your k8, in stock trim it would run with the 69 all day long. Imagine what it can really do know after your work on it.

But still, have fun with your carbs and good luck if you are putting together a sandcast, parts can be hard to find and expensive but the end result is worth it.

[Piute]

                         I've alway's like that read but
  THIS paragraph;....( catches my interest most )needed the pluses ,yet old too
     Let’s examine the F2 Super Sport first. Visually it comes on like a left hook. Long, lean, black, sporty, shiny, and put together so no one would suspect its styling is a toupee to conceal balding. There’s no question that it’s built for young, aggressive riders who wouldn’t think of diluting the image with saddlebags or a fairing. The shapes and lines of the ’76 model are barely recognizable in the new execution. The blackness is pierced by chrome cover plates and sparkling pipes, but the dominant contrast comes from the wheels. Ah yes, the wheels.

           
                                                Guess I'm Old,and don't think
                                                      I did leave the wheels just two toned them

                                                                                     

[Lucky 1]

I am not building a KO model.

Your info about the 1/4 mile times is very interesting!

I still have my 78 carbs on my 78 bike.
I was thinking about putting the 1969 carbs on the 1978, but now that my 1978 carbs seem to be working well I may just rehab the 1969 carbs and sell them.
The only problem I had on my 1978 was the throttle would get hung up and not come down to low idle occasionally.
So I have just replaced the throttle and both push and pull cables with new OEM stock cables and a brand new Motion Pro push pull throttle. That should solve the problem.

Thanks for digging up all that useful info!!

[Re-run]

I got the motion pro cables and They gave me binding issues after just a few years. It was like the second cable got shorter somehow. Before that, they worked great. I haven't replaced them yet, I disconnected that cable and left it hang. Now things snap back shut like they should and I have the second cable for emergency.