Topic: Throttle 1 into 4 problems

[Sandy]

Howdy everybody:

My 1969 750 was almost finished when I received the carbs back from www.motorcycleproject.com last Friday.  I had no trouble installing them, went on very easy with the new insulators, but did not install the airbox or anything else until I was sure I had the throttle hookup complete.  While I am very familiar with the push/pull throttles made by Honda, I am totally confused by the 1 into 4.  My problem now is while trying to install the throttle to the right handgrip, I lost all the push/pull motion for the slides.  Today I removed the carbs and I still cannot get the push/pull to work with the carbs removed from the motor.  At the carb tops, the slides work perfectly by pulling on the respective cable, opening and closing easily.  What I cannot do is to move the slides from the opposite end of the throttle cable.  Any help or advice will be greatly accepted.  Thanks to all in advance.

[Xnavylfr]

If I remember right ,each carb had a spring that sat on top of the slides ,when you opened the throttle those springs compressed and release the throttle the springs was what closed the slides and I didn't remember but 1 cable from the throttle grip down to the intersection where the 4 cables slid in to the 4/1 adapter. I could be WAY off here because it's been a hundred years since I worked on a SANDY. Maybe not a HUNDRED!!!


Xnavylfr(CHUCK)

[Sandy]

Xnavyflr:

Thank you for the response.  Yes, there are springs inside each carb that will do the return thingie-dooie, and this particular side of the 4-1 works fine.  It is just that the 1 cable from the grip will not move either of the four cables headed for the carbs. Maybe this pic will help.  If I try to manually push the cable in, nothing happens, kinda like something is stuck, as there is no movement with the slides.  Again, the slides work smoothly by moving the individual cables that are attached to the top of the carbs.  This is baffling to me because before I installed the carbs, the push/pull cable worked just fine .  God Bless Mother Honda.

[Xnavylfr]

Inside that connector there should be a slider with a single hole in the middle for your pull cable and 4 notches that the carb cables slide in to.  That interconnect HAS to slide freely inside that sleeve. If it slides freely , then open the throttle sleeve clamp (where pull cable goes in) and make sure you have it in the right position. Sometimes the cable will be out of the channel and bind the throttle.


Xnavylfr(CHUCK)

[754]

Your 1 And 4 look kinked..if that gets turned the wrong way, it may hang things up.

[bjbuchanan]

Reaching, but is the cable good? The upper 1 portion I mean. It looks in nice shape but is it old/unknown origin just cleaned up?

Oh and I have seen plenty of mention that the 4-1 cable was very particular about the cable routing

[Sandy]

Howdy all:

bjbuchanan:  I was told by the Motorcycle Project people that the cable is a brand new Honda 4-1 cable and I have no reason to doubt their word. As to the routing, I am brain dead on this.  To me the 4 cables need to go under the frame as they will not clear the coil package at all - am I incorrect on this also?  If I do, the 1-4 carbs cables seem binding.

754:  I kinda agree with you that 1 & 4 do not look kosher to me either.  Also (story later) when I pull the 1 cable from the grip end, the 2-3 carbs open later than 1-4 carbs - that does not make sense to me as I must have routed the cables incorrectly.

Xnavyflier:  Your description is exact and there is no binding in the connection, but to me the pull to open the 4 carbs is way too hard (story next).

First, thank you all for your responses, I do appreciate all of them.  Now, getting old comes at a bad time.  I have spent two days off and on trying to figure out why I can't see how this works.  Well, I had a brilliant idea - I used a pair of pliers on the grip portion of the 1 cable and the slides all worked, I just couldn't do this by hand.  So, by pulling on this end of the cable, 1-4 opened first and 2-3 opened later - something that I think is incorrect as well as the pull necessary to open the slides.  Attached pic shows the result.
So, I will try to fix the grip end of the cable and see what happens.  The springs inside each carb was really light in tension, so I think that something is binding inside those 4 cables making the pull so hard.  I will keep everyone posted as to the results.
Lastly, can anybody show me the routing of this cable? Under/over frame?

[Dream750]

This service bulletin/recall briefly touches on the K0 cable routing and frame modification:

http://manuals.sohc4.net/CB750SB/750_15.pdf

[70CB750]

I am late to the party - but  I have 1-4 working flawlesly on my K0, please do not hesitate to ask if you have more questions/problems.

[lucky]

I can explain everything you need to know about these carbs and this throttle cable.

It is a PULL only cable.

I can also tell you a way to set these carbs up that will make it easy to tune them.

These 1969-70 carbs are the best as far as I am concerned.
The reason is they do not have lifter arms or throttle shafts and you can EASILY get to all adjustments. ALL adjustments. The choke is a simple lever.
All of the jets are easy to get to. This important if you need to see if the idle jets are clogged.
The float bowl had a simple clip to easily remove the float bowl instead of 4 screws.


The idle screw actually raises and lowers the slide.
The idle thumb adjustment wheel even has a mark on it shaped like a letter "T" so that you can set all 4 carb slides the same.
Turn those screws so that the top of the letter "T" is visible and close to the body of the carb. If you turn it in too far the top of the letter"T" will dissapear into the body of the carb. Back it off until you can see the whole letter "T" mark.
IF you are not ham fisted you can actually feel the idle adjust knob contact the slide when turned, and feel the resistance.


Set all 4 of the pilot air screws to exactly one full turn.


Install the carbs.
Make sure to NOT repeat NOT put any restraints on the throttle cable to tie it down
to the frame. See third photo down below.

Male sure all cables flow freely to the carbs. Get the cylindrical cable junction box centered in the frame on top of the engine. (under the coils)

Turn the adjusters on the TOP of the carbs so that there is no slack in the cable.
Otherwise when you turn the throttle the carb that you are adjusting immediately starts to move the slide up exactly when you start to turn the throttle.
Do this on all 4 carbs.

Make sure that when you turn the throttle open, that all 4 slides start to move at the same exact time.
Make sure that the part of the throttle cable between the throttle and the throttle cable junction box has the adjuster turned in so that the throttle has about 1/4 inch of play before it starts to pull on the throttle cables.

Attach your sync gauges.
Start the engine.
Get it warmed up.

Then using ONLY the idle thumb screws get all the sync gauges to read the same amount and keep the idle down to about 1000-1200 RPM.

When that is completed use the adjuster on the throttle cable near the throttle to adjust the idle.
With this method you can easily adjust the idle of all 4 carbs with this one adjuster any time you need to. Like winter and summer etc.


Remember do NOT try to restrain the throttle cable junction box!!

I was a Honda Dealer mechanic at the time these carbs were first introduced.

 Click on the photos below for a larger version.

[754]

There were 2types of cables, i think the first were thinner od, and a bit shorter on length. They changed as they were having some issues.

 Iff you uncrew the slides from the bodies..does it then work smoothly..if so it sounds like a routing problem. Hope a KO owner explains that as there are a few variables that can bite you.

[lucky]

There were 2types of cables, i think the first were thinner od, and a bit shorter on length. They changed as they were having some issues.

 Iff you uncrew the slides from the bodies..does it then work smoothly..if so it sounds like a routing problem. Hope a KO owner explains that as there are a few variables that can bite you.

The issue was corrected when Honda made the two outside cables from the junction box to the two outside carbs longer.

[lucky]

Do you have the right throttle? The ramp configuration is important to have leverage.

[Sandy]

Howdy again:

For all of you that responded, thank you very much.

Dream750 - I printed out your Honda Technical Bulletin and now know the proper routing.  Again this was my mistake.  When I sent the carbs to The Motorcycle Project, I sent them bare - no throttle cables as I had removed them.  The technician said he needed the 4-1 cable, so I sent him the old one.  Basically, he said it was shot and he then purchased a new Honda throttle cable and installed this new cable on all 4 carbs.  Had I known the routing, I would have told him to do only the 2-3 carbs and I would do the 1-4 carbs.  My mistake and I will get a new throttle cable and install these carbs properly.

lucky:  For what its worth, I have the original Honda CB750 shop manual and while it goes into good detail, as with most shop manuals, a lot of stuff is not mentioned.  Your response totally cleared up the problems I have and I believe there is nothing better than experience, so thanks for the detail.  I have a sync gauge set ( I have 3 CBX's) that I will use to set the carbs properly - pic attached.  I will follow your instructions and let all responders know how well it came out.  If it doesn't work, I'm coming to Guerneville .

Thanks again to all people interested in this "project"

[lucky]

Howdy again:

For all of you that responded, thank you very much.

Dream750 - I printed out your Honda Technical Bulletin and now know the proper routing.  Again this was my mistake.  When I sent the carbs to The Motorcycle Project, I sent them bare - no throttle cables as I had removed them.  The technician said he needed the 4-1 cable, so I sent him the old one.  Basically, he said it was shot and he then purchased a new Honda throttle cable and installed this new cable on all 4 carbs.  Had I known the routing, I would have told him to do only the 2-3 carbs and I would do the 1-4 carbs.  My mistake and I will get a new throttle cable and install these carbs properly.

lucky:  For what its worth, I have the original Honda CB750 shop manual and while it goes into good detail, as with most shop manuals, a lot of stuff is not mentioned.  Your response totally cleared up the problems I have and I believe there is nothing better than experience, so thanks for the detail.  I have a sync gauge set ( I have 3 CBX's) that I will use to set the carbs properly - pic attached.  I will follow your instructions and let all responders know how well it came out.  If it doesn't work, I'm coming to Guerneville .

Thanks again to all people interested in this "project"

You will be fine.

I also like visitors though! LOL...lol

Remember use the idle knobs to sync the carbs.
Do not move the mixture screws while you sync the carbs.
You might have to turn those mixture screws back to 3/4 .
AFTER THE CARBS ARE IN SYNC.
Depends how worn out the carbs are.
Those mixture screws on those carbs are very sensitive to adjustment unlike the later models.
Also remember you can turn that throttle cable adjuster up at the throttle outwards to get it to idle if you need to.
Once it starts to run decent you can keep turning the idle down and rebalance the carbs until it idles at about 1000-1200 rpm.

Please report back to let us know that you got good results.

[Sandy]

Howdy all:

While waiting for the new cable to come in, I decided to "mock up" some things that I have learned from those of you that responded as well as anyone else who might be interested in watching.  I have attached 4 pics to show the left side, the right side, the top side and a full left side views of where I am now.   Lucky - I noticed your insulators were much shorter than mine and was wondering that since you have a different airbox or a newer Honda, is that the reason?  Every on eBay said the sandcast insulators were different, but the ones I purchased are exactly the same as the insulators I removed from the original motor. I know about eBay and when it comes to Honda 750's, everything seems to be sandcast , so I need to know exactly for what I am looking.  Anyway, any comments will be happily received.  Here are the pics.

[lucky]

My "insulators"(carb mount boots) are shorter. They are for a 1978 engine.
Do not pay any attention to that.

Can you post a photo of the cable junction box in situ?

[Sandy]

lucky:

The 4-1 cable that I ordered was supposed to come in Monday, only included in the shipment box were 4 carb boots , not the cable.  The supplier said they sent a cable out to me yesterday, so it will be here later this week.  I wanted to hook up all 4 carbs, do the routing without hooking up the grip and send you an accurate pic.  Thank you for your support.

[lucky]

lucky:

The 4-1 cable that I ordered was supposed to come in Monday, only included in the shipment box were 4 carb boots , not the cable.  The supplier said they sent a cable out to me yesterday, so it will be here later this week.  I wanted to hook up all 4 carbs, do the routing without hooking up the grip and send you an accurate pic.  Thank you for your support.

You can still go ahead and mount the carbs.
Those carbs can have the slides easily removed, even on the bike.

[Don R]

I wonder if I should take mine in for the recall? it's a 10141xx

[lucky]

I wonder if I should take mine in for the recall? it's a 10141xx

I would not trust the mechanics they have now at those dealerships because they know nothing about these bikes.

[Sandy]

Why, it is yet another update !!!!

Throttle cable finally came in and I got to work on their installation.  Took some pics, several attached, to show everybody watching this thread.  I hooked up the throttle cable to carbs #2 and 3; installed the complete carb set and then hooked up the cable to carbs #1 and 4. Not a big deal, but I did fumble around a bit .  Routed the 4-1 through the frame and on to the grip but I did not hook the cable to the grip.  The pull to open all four carbs is still too rough, even though I can open all 4 of them.  I will take the cap off the cable, put some oil down to where the 4 cables hook up and see if that helps.

Lucky and anyone else watching/commenting - if you have any comments, I would love to hear them.

Thanks again to all.

[HondaMan]

By hand, it is REAL hard to pull open all 4 cable carbs at once. The grip twist yields a 16:1 ratio in your favor, though. I had to make a metal pull-handle to test the last cable set I rebuilt for one of our own in GA, I couldn't pull it by fingers. I made a steel bar, 1/4" x 1", with a hole drilled near one end and ground a little groove out of the hole to let the cable lie through it. To "block" the cable sheath, I drilled a similar hole in a piece of wood so I could play Superman and pull them apart. But, then it pulled much easier!

[70CB750]

Looks like you are in good shape, I think my 1 cable goes on the right side of the steering head, but I could be wrong.

[lucky]

Looks like you are in good shape, I think my 1 cable goes on the right side of the steering head, but I could be wrong.

Yes that is correct.

You can put 1 very loose cable tie up by the front forks just to keep the throttle cable from flying out and snagging on something but do not put any tight cable ties on that throttle cable.
The cable junction box should be on top of the engine valve cover but underneath the coils.