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Author Topic: 78 cb 750k carb question  (Read 1613 times)

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Offline bultaco59

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78 cb 750k carb question
« on: February 01, 2013, 06:34:52 AM »
Hello gentlmen, I know Im asking alot of questions,this being my first sohc 4
Ok heres the deal, I gots carb apart, and there ready to soak, when I took them
apart, there is this big diafram, with linkage that connects to the main shaft
with hoses that connect to the carb, and to this switch of some sort that has
electircal connections (2 wires)that plug somewhere on the wiring harness.
1. What the hell is it ? 2. Do I need this. on reasssembly I would like to leave
all of this off, I m guessing its smog stuff. has anybody seen this stuff. I sorry
theres no pictures, but Im at work.

Thank You
Bob in Burbank
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Offline flybox1

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Re: 78 cb 750k carb question
« Reply #1 on: February 01, 2013, 06:55:21 AM »
Quote from: bultaco59 on February 01, 2013, 06:34:52 AM
Hello gentlmen, I know Im asking alot of questions,this being my first sohc 4
Ok heres the deal, I gots carb apart, and there ready to soak, when I took them
apart, there is this big diaframACCEL PUMP DIAPHRAGM, with linkage that connects to the main shaft ACCEL PUMP SHAFT with hoses that connect to the carb, and to this switch of some sort that has
electircal connections (2 wires)that plug somewhere on the wiring harness.  NO CLUE
1. What the hell is it ? 2. Do I need this. on reasssembly I would like to leave
all of this off, I m guessing its smog stuff. has anybody seen this stuff. I sorry
theres no pictures, but Im at work.

Thank You
Bob in Burbank

Yes, you'll need the accel pump components.  they help 'prime' the throats of the carbs with fuel for easier starts.   The diaphragm cup fills with gas, and with the first 1/4 throttle movement shoots the fuel into the accel pump system.  the fuel travels through passages and tubes(see below, pink tubes w brass inserts) in between carbs, and out these small brass injector posts which can be seen in the photos below.  they can create a good spray of gas to get you going from a full stop.  as for the rest of the 'electrical' stuff....i got nothing  ;D
« Last Edit: February 01, 2013, 06:57:05 AM by flybox1 »
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'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

Past Bikes
1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

"This is my CB. There are many like it, but this one is mine…"

Offline toytuff

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Re: 78 cb 750k carb question
« Reply #2 on: February 01, 2013, 06:55:57 AM »
Where in the pictures?

tt
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Offline bultaco59

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Re: 78 cb 750k carb question
« Reply #3 on: February 01, 2013, 07:40:31 AM »
Its not in the pictures, it is also not the acel pump that is on carb, this is a whole
seperate unit that sits on top of the carbs. it appears to be a diafram like said
coming out of the bottom a arm, that does not push the main shaft, it is accually connected to a arm on tha main shaft. it is about 2 in in dia. the other component
look like a air sw like on a smog system (sensor?)
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Offline flybox1

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Re: 78 cb 750k carb question
« Reply #4 on: February 01, 2013, 07:52:50 AM »
post pictures when you can..
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'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

Past Bikes
1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

"This is my CB. There are many like it, but this one is mine…"

Offline bultaco59

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Re: 78 cb 750k carb question
« Reply #5 on: February 01, 2013, 07:57:06 AM »
Ok when I get home.
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Offline stewonepot

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Re: 78 cb 750k carb question
« Reply #6 on: February 01, 2013, 08:16:03 AM »
Hi All,
Is possible his carbs come from an auto?
Regards Stew.

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Offline mrrch

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Re: 78 cb 750k carb question
« Reply #7 on: February 01, 2013, 08:25:42 AM »
The Automatics have a solenoid on the carbs.
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my build

1977 CB750K WITH 1976 CB750F ENGINE

Offline stewonepot

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Re: 78 cb 750k carb question
« Reply #8 on: February 01, 2013, 08:39:23 AM »
Which would explain the wires maybe?
regards Stew
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Offline flybox1

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Re: 78 cb 750k carb question
« Reply #9 on: February 01, 2013, 10:22:04 AM »
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'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

Past Bikes
1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

"This is my CB. There are many like it, but this one is mine…"

Offline flybox1

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Re: 78 cb 750k carb question
« Reply #10 on: February 01, 2013, 05:57:58 PM »
 Ha...we've got 2 threads going on here.
Get rid of those 750A carbs, and find some PD's.
Might want to contact member sohcdigger for a set...you'll be happy later...
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'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

Past Bikes
1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

"This is my CB. There are many like it, but this one is mine…"

Offline toytuff

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Re: 78 cb 750k carb question
« Reply #11 on: February 01, 2013, 07:16:33 PM »
Quote from: mrrch on February 01, 2013, 08:25:42 AM
The Automatics have a solenoid on the carbs.

AaHa!

tt
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Offline Gordon

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Re: 78 cb 750k carb question
« Reply #12 on: February 02, 2013, 06:39:07 AM »
I'll lock this duplicate thread.  Please use the other one for further discussion on this topic.
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