Author Topic: throttle cable  (Read 1907 times)

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who_iz_phil

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throttle cable
« on: April 21, 2010, 03:42:02 PM »
so just to be sure, from what i have read, i am supposed to have two throttle cables on a 1978 cb750k(push pull), this beast that i just bought to do a cafe build (it is a bucket, been sitting for 15 years or so)  only has one cable but it has a spot for the other, did some only come with one cable or has someone taken the other off at some point in time. i'm asking because i need new one(s) and not sure to get the two setup or one( i see listings for both setups online) thanks for reading and any expertise is appriciated!!!!!!

Offline MCRider

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Re: throttle cable
« Reply #1 on: April 21, 2010, 06:00:23 PM »
so just to be sure, from what i have read, i am supposed to have two throttle cables on a 1978 cb750k(push pull), this beast that i just bought to do a cafe build (it is a bucket, been sitting for 15 years or so)  only has one cable but it has a spot for the other, did some only come with one cable or has someone taken the other off at some point in time. i'm asking because i need new one(s) and not sure to get the two setup or one( i see listings for both setups online) thanks for reading and any expertise is appriciated!!!!!!
It had two. The "B" return cable is a safety feature and does nothing if the throttle is otherwise in good working order. It is along for the ride.

If anything in the "A"cable fails, like it gets hung up, the return spring fails etc, the B cable allows you to force the carburetors, or at least the throttle butterflies, closed. Your carbs have the chance I think of the CV slides to hang up anyway. Very remote possibilities.

It has been the subject of many threads here, whether one can be comfortable running an A only setup or not. It is the sort of discussion as helmets, lights on, etc. Sure you can do without it, but should you. Personal choice in my book. The CB750 introduced the dual cable setup to most of the civilised world IIRC.  others may have had it, but not in the volume of the CB750.  The pre-K1 models had a single cable setup. Many bikes, customs, etc still do.
« Last Edit: April 21, 2010, 06:03:55 PM by MCRider »
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Offline eurban

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Re: throttle cable
« Reply #2 on: April 21, 2010, 06:13:24 PM »
77/78 carbs are slide type not CVs.  The b cable is there to pull the slide shut if the spring fails or doesn't have the oomph.  Not much expense or effort is required to replace this cable and its a useful safety feature . . .

Offline 8 Track

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Re: throttle cable
« Reply #3 on: April 21, 2010, 06:15:02 PM »
I ran one cable (the way po had it set up) for years.  Never liked it, but never had a problem.  Since I didn't like always thinking about my kill switch, I coughed up the cash and bought the other cable.  Now I can concentrate on the road.  Once you have a carb or four hang open, you'll never do without two cables again, imho.  
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Offline MCRider

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Re: throttle cable
« Reply #4 on: April 21, 2010, 06:17:18 PM »
77/78 carbs are slide type not CVs.  The b cable is there to pull the slide shut if the spring fails or doesn't have the oomph.  Not much expense or effort is required to replace this cable and its a useful safety feature . . .
I thought I'd get corrected on that one. Are any CB750 carbs CV types? Just curious.
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1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
"Sometimes the light's all shining on me, other times I can barely see, lately it appears to me, what a long, strange trip its been."

who_iz_phil

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Re: throttle cable
« Reply #5 on: April 22, 2010, 10:50:57 AM »
thanks guys..... i guess someone removed the other at some point in time, the throttle dosen't move at all now, cable rusted, like i said, been sitting for about 15 years, i just wanted to be sure which i needed to buy to replace it. Thanks again!!!!!

Offline eurban

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Re: throttle cable
« Reply #6 on: April 22, 2010, 03:35:15 PM »
77/78 carbs are slide type not CVs.  The b cable is there to pull the slide shut if the spring fails or doesn't have the oomph.  Not much expense or effort is required to replace this cable and its a useful safety feature . . .
I thought I'd get corrected on that one. Are any CB750 carbs CV types? Just curious.

No, the only SOHC with cv carbs are the last couple years of the sohc 650.  Not sure what year the DOHC 750s started using CV carbs  . . .

Offline MCRider

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Re: throttle cable
« Reply #7 on: April 22, 2010, 06:12:20 PM »
77/78 carbs are slide type not CVs.  The b cable is there to pull the slide shut if the spring fails or doesn't have the oomph.  Not much expense or effort is required to replace this cable and its a useful safety feature . . .
I thought I'd get corrected on that one. Are any CB750 carbs CV types? Just curious.

No, the only SOHC with cv carbs are the last couple years of the sohc 650.  Not sure what year the DOHC 750s started using CV carbs  . . .

Thanks.
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Ron
1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
"Sometimes the light's all shining on me, other times I can barely see, lately it appears to me, what a long, strange trip its been."

Offline BobbyR

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Re: throttle cable
« Reply #8 on: April 22, 2010, 06:22:15 PM »
I just replaced both cables with OEM Honda. When you grab for brake, you palm closes the carbs shut. Also when i hve the choke on my 78K has a fast idle feature, I can knock the RPMs down low and shift in gear. The push cable really closes the carbs down. Once you have two new cables and have everything smooth, you realize that spring is not that strong.
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Offline MCRider

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Re: throttle cable
« Reply #9 on: April 23, 2010, 06:53:37 AM »
I just replaced both cables with OEM Honda. When you grab for brake, you palm closes the carbs shut. Also when i hve the choke on my 78K has a fast idle feature, I can knock the RPMs down low and shift in gear. The push cable really closes the carbs down. Once you have two new cables and have everything smooth, you realize that spring is not that strong.
I'm open for correction here. But my understanding of the system is that if the B cable is doing anything then your throttle is not set up properly, is hanging up, or the spring is failing. The spring should be "ahead" of the B cable thoughout the closing motion including putting the slides completely down to idle. You should be able to remove the B cable and notice no change.

The exception may be in overriding the fast idle which comes with the choke which the early bikes don't have.
Ride Safe:
Ron
1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
"Sometimes the light's all shining on me, other times I can barely see, lately it appears to me, what a long, strange trip its been."

Offline BobbyR

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Re: throttle cable
« Reply #10 on: April 23, 2010, 08:02:19 AM »
I just replaced both cables with OEM Honda. When you grab for brake, you palm closes the carbs shut. Also when i hve the choke on my 78K has a fast idle feature, I can knock the RPMs down low and shift in gear. The push cable really closes the carbs down. Once you have two new cables and have everything smooth, you realize that spring is not that strong.
I'm open for correction here. But my understanding of the system is that if the B cable is doing anything then your throttle is not set up properly, is hanging up, or the spring is failing. The spring should be "ahead" of the B cable thoughout the closing motion including putting the slides completely down to idle. You should be able to remove the B cable and notice no change.

The exception may be in overriding the fast idle which comes with the choke which the early bikes don't have.
I have a K8 so the situation is different. I opted for two cables for safety and actually bike control. If I release the grip the throttle closes on it's own via the spring the B cable does nothing.
When the choke is out I can momentarily drop the RPMs using the B cable to force the slides closed. Handy, but not a major value proposition. I ride on semi rural roads in a hilly area.

I realized that I am always making throttle adjustments and I can
maintain a stable grip and use the A&B cables to get an instant engine response since just by flexing my wrist and not changing my hand position on the grip itself.

All of these add up to my decision to stay with two cables.   
Dedicated to Sgt. Howard Bruckner 1950 - 1969. KIA LONG KHANH.

But we were boys, and boys will be boys, and so they will. To us, everything was dangerous, but what of that? Had we not been made to live forever?

Offline MCRider

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Re: throttle cable
« Reply #11 on: April 23, 2010, 08:17:25 AM »
I just replaced both cables with OEM Honda. When you grab for brake, you palm closes the carbs shut. Also when i hve the choke on my 78K has a fast idle feature, I can knock the RPMs down low and shift in gear. The push cable really closes the carbs down. Once you have two new cables and have everything smooth, you realize that spring is not that strong.
I'm open for correction here. But my understanding of the system is that if the B cable is doing anything then your throttle is not set up properly, is hanging up, or the spring is failing. The spring should be "ahead" of the B cable thoughout the closing motion including putting the slides completely down to idle. You should be able to remove the B cable and notice no change.

The exception may be in overriding the fast idle which comes with the choke which the early bikes don't have.
I have a K8 so the situation is different. I opted for two cables for safety and actually bike control. If I release the grip the throttle closes on it's own via the spring the B cable does nothing.
When the choke is out I can momentarily drop the RPMs using the B cable to force the slides closed. Handy, but not a major value proposition. I ride on semi rural roads in a hilly area.

I realized that I am always making throttle adjustments and I can
maintain a stable grip and use the A&B cables to get an instant engine response since just by flexing my wrist and not changing my hand position on the grip itself.

All of these add up to my decision to stay with two cables.   
Ah unnerstan.   :)
Ride Safe:
Ron
1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
"Sometimes the light's all shining on me, other times I can barely see, lately it appears to me, what a long, strange trip its been."

Offline Duke McDukiedook

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Re: throttle cable
« Reply #12 on: April 23, 2010, 08:22:20 AM »
Hey, plus the fact that if your A fails, you can switch the B until you can get another A.
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