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Author Topic: 1978 honda cb750 carb help.  (Read 1062 times)

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Offline briancwynn

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1978 honda cb750 carb help.
« on: September 04, 2014, 04:40:18 AM »
All, as a mechanically challenged individual I don't know what to do with the carbs. They have to be cleaned thoroughly and I don't think I can do it. With that said it would be around 400 bucks around here to have someone do it. Should I buy the new racing carbs for 800 bucks and save the hassle? I have no plans on racing as well as it is only a weekend rider. Should I man up and try and do the carbs?
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Honda CB750 1978 K
Stock Carbs w/ Pods
125 main jets, stock slow, and 2 shims on the needle (equal to about raising it one clip)
M-unit
Bike broken down to bare bones and slowly put back together (except for the engine)

Offline flybox1

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Re: 1978 honda cb750 carb help.
« Reply #1 on: September 04, 2014, 06:59:33 AM »
many have sent carbs to harisuluv to have carbs cleaned and ready to use, but he wasnt around when i started working on carbs.
I had to figure it out myself, and it turns out it wasnt that hard.  youre still going to need to understand the components for tuning purposes.   might as well try it yourself, first.   
you wont need to separate the carbs from eachother and off of the mounting plate, but you will need to take the bowls and the top caps off, and with some cleaning impliments, scrub it clean of all debris and varnished gas.  do one carb at a time, take something off clean it well, and set it aside.  everything goes back on in the reverse order it came off. 
not to take anything away from harisuluv, as his work is reported as exceptional, i say do it yourself. 
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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 Maurice

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Re: 1978 honda cb750 carb help.
« Reply #2 on: September 04, 2014, 07:12:22 AM »
Second that, you shouldn't have to separate the carbs to clean them. As long as you don't open the tops you shouldn't even have to sync., that is, if the slides move freely leave them alone.

Definitely feasible on your own. The only hard part is getting the pilot jets out without damaging them: hey are pressed in. Just pull straight out and carefully, they come out eventually. It's important they're clean because they have small holes on the sides to help atomize fuel.

Thorough cleaning of all the passages gas goes through should do it: stick a tube in each orifice and blow compressed air/carb cleaner. I like to use copper strands through the jet openings so as not to damage them, so far has worked very well.

That being said I am a firm believer in self-cleaning carbs by simply riding the bike (flame away...). Gas is a solvent after all. I've had carburetor issues clear up just by riding, but of course real gunky carbs should be cleaned by hand.

Good luck.
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Offline briancwynn

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Re: 1978 honda cb750 carb help.
« Reply #3 on: September 04, 2014, 08:37:12 PM »
Thanks all for the suggestions but I think the first time I will have someone do them the suggested user. With that said if I dont want to use the OEM air box what do you suggest to replace it with?  I see that the pods get ripped on the forum.  Any other ideas?
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Honda CB750 1978 K
Stock Carbs w/ Pods
125 main jets, stock slow, and 2 shims on the needle (equal to about raising it one clip)
M-unit
Bike broken down to bare bones and slowly put back together (except for the engine)

Offline flybox1

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Re: 1978 honda cb750 carb help.
« Reply #4 on: September 04, 2014, 08:44:47 PM »
The question you should be asking is...
Do I want easy and correct jetting settings and a properly running bike with an.Ken airbox, or do I want a few weeks, or more, of trial and error.jetting, for carbs I don't really know a lot about, to maybe get a properly running bike with pods?
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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 briancwynn

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Re: 1978 honda cb750 carb help.
« Reply #5 on: September 05, 2014, 08:20:04 AM »
All,  http://www.steeldragonperformance.com/contact_us_3.html  will these require alterations to the carbs?  These look much better than stock. Or the Uni KN airbox that Calj737 i dont understand how that is installed on the bike.  Im dumb! 
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Honda CB750 1978 K
Stock Carbs w/ Pods
125 main jets, stock slow, and 2 shims on the needle (equal to about raising it one clip)
M-unit
Bike broken down to bare bones and slowly put back together (except for the engine)

Offline flybox1

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Re: 1978 honda cb750 carb help.
« Reply #6 on: September 05, 2014, 08:22:38 AM »
anthing other than stock will require alterations to the carbs.
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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 briancwynn

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Re: 1978 honda cb750 carb help.
« Reply #7 on: September 05, 2014, 09:40:15 AM »
Love this. Thank you for the insight.  I will put the original back on. You would think someone would create something that doesn't look like Xanadu.  Thanks again.
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Honda CB750 1978 K
Stock Carbs w/ Pods
125 main jets, stock slow, and 2 shims on the needle (equal to about raising it one clip)
M-unit
Bike broken down to bare bones and slowly put back together (except for the engine)

Offline briancwynn

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Re: 1978 honda cb750 carb help.
« Reply #8 on: September 12, 2014, 09:49:13 AM »
Since I am going to use the stock airbox . Has anyone ever painted the air box with good results. I'm thinking if I paint it to match the side covers it might flow better looks wise? Not sure about painting plastic.
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Honda CB750 1978 K
Stock Carbs w/ Pods
125 main jets, stock slow, and 2 shims on the needle (equal to about raising it one clip)
M-unit
Bike broken down to bare bones and slowly put back together (except for the engine)

Offline flybox1

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Re: 1978 honda cb750 carb help.
« Reply #9 on: September 12, 2014, 10:14:55 AM »
sand it with 1500wet, and then treat it with Mothers Back to Black.
it'll look like new  ;)
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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 briancwynn

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Re: 1978 honda cb750 carb help.
« Reply #10 on: September 12, 2014, 10:29:32 AM »
Fly I don't want it to be black. I have used back to black and that stuff works great. I want to paint it cream colored to match the tank and the side covers. Some plastics just don't paint well.
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Honda CB750 1978 K
Stock Carbs w/ Pods
125 main jets, stock slow, and 2 shims on the needle (equal to about raising it one clip)
M-unit
Bike broken down to bare bones and slowly put back together (except for the engine)

Wobbly

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Re: 1978 honda cb750 carb help.
« Reply #11 on: September 12, 2014, 10:57:14 AM »
@briancwynn
As a side note: I am glad that you like my bike so much that you use my picture of my bike as your avatar.
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Offline flybox1

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Re: 1978 honda cb750 carb help.
« Reply #12 on: September 12, 2014, 10:58:19 AM »
as much as it might look good, you'll have your airbox in and out more than a bunch of times, and its not the simplest to get in and out.  everytime you bump it on something, the soft plastic wont hold the paint and you'll have a mark or a chip.
just something to think about.....
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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: 1978 honda cb750 carb help.
« Reply #13 on: September 12, 2014, 10:59:16 AM »
Quote from: Wobbly on September 12, 2014, 10:57:14 AM
@briancwynn
As a side note: I am glad that you like my bike so much that you use my picture of my bike as your avatar.

HAHAHAHA!!!
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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 briancwynn

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Re: 1978 honda cb750 carb help.
« Reply #14 on: September 12, 2014, 11:18:51 AM »
Wobbly ...the highest form of flattery!!!!  If it wasn't yours it was going to be someone else's.  I loved it.
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Honda CB750 1978 K
Stock Carbs w/ Pods
125 main jets, stock slow, and 2 shims on the needle (equal to about raising it one clip)
M-unit
Bike broken down to bare bones and slowly put back together (except for the engine)
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