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Offline oldk6guy

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carb gurus need your help
« on: July 10, 2013, 10:23:07 PM »
I'm about to embark on the journey of rebuilding my carbs. Never done it before. I have the four carb rebuild kits I need...I think. I have a spare set of 75 cb750 carbs and kits for those carbs. The plan is to rebuild those and put them on my 76 cb750. My questions are what are the differences between 75 and 76 carbs and what jet size I would need for my bike. Bike is 76 cb750 with cycleX drag pipes and carbs have air horns with only screens to filter. I do have the stock air box as well. Thanx in advance.
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76 cb750 k6: 4 into 4 exhaust, open air horns on carbs.

Offline goldarrow

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Re: carb gurus need your help
« Reply #1 on: July 10, 2013, 11:26:20 PM »
Don't know what jet sizes are, manual is good for that, but these 750 carbs are fairly easy to work with.
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Offline disco

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Re: carb gurus need your help
« Reply #2 on: July 11, 2013, 02:27:47 AM »
Hi Streetfighter,
I did a similar thing. I've also got a CB750 K6 & temporarily fitted a set of carbs from an earlier model (K2/3/4?) whilst I rebuilt my K6 carbs. The bike ran much better than it had for a while. The K6 carbs were badly clogged up. The only problem I encountered was that the idle throttle stop was now on the left side & it was hidden behind the fuel petcock. This made it difficult to adjust the idle up on a cold start. The K6 carbs have now been rebuilt & are back on. They feel even better. I'm running #40 pilots & #110 mains...seems to work OK.
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Offline oldk6guy

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Re: carb gurus need your help
« Reply #3 on: July 11, 2013, 06:24:22 AM »
THERE'S AN IDLE THROTTLE STOP?!?!? where is this glorious contraption on my k6? adjusting this will probably allow my bike to idle without dying?
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76 cb750 k6: 4 into 4 exhaust, open air horns on carbs.

Offline oldk6guy

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Re: carb gurus need your help
« Reply #4 on: July 11, 2013, 06:44:06 AM »
found it...now she idles....that makes me happy!
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76 cb750 k6: 4 into 4 exhaust, open air horns on carbs.

Offline oldk6guy

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Re: carb gurus need your help
« Reply #5 on: July 11, 2013, 10:56:26 AM »
Sooooo...110 and 40 then, I guess???
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Offline Bankerdanny

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Re: carb gurus need your help
« Reply #6 on: July 11, 2013, 10:59:36 AM »
If you call or e-mail Cycle-X I would bet they would suggest a starting point for you.
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Offline oldk6guy

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Re: carb gurus need your help
« Reply #7 on: July 11, 2013, 11:13:40 AM »
hmm. i'll give that a try. thank you.
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Offline Silverback

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Re: carb gurus need your help
« Reply #8 on: July 11, 2013, 12:47:27 PM »
http://www.motorcycleproject.com/motorcycle/text/specs.html

Without a dyno, the only proper way to tune your carbs is by riding it and dialing it in. This is made easier by doing plug chops. Good luck!!
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Offline lucky

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Re: carb gurus need your help
« Reply #9 on: July 11, 2013, 10:26:26 PM »
Quote from: k5streetfighter on July 10, 2013, 10:23:07 PM
I'm about to embark on the journey of rebuilding my carbs. Never done it before. I have the four carb rebuild kits I need...I think. I have a spare set of 75 cb750 carbs and kits for those carbs. The plan is to rebuild those and put them on my 76 cb750. My questions are what are the differences between 75 and 76 carbs and what jet size I would need for my bike. Bike is 76 cb750 with cycleX drag pipes and carbs have air horns with only screens to filter. I do have the stock air box as well. Thanx in advance.

No problem with carb mounting. They are almost the same.
I liked the 76's because the idle return spring was centered.

Velocity stacks and 4 into one pipes? OR are they 4 into 4? No baffles right?

Stock #110 mains 1975
#40 Idle jets
Needle clip position 4th down from the top.


My suggestion.
#120 main jets.
#42 idle jets.
Needle clip position 4th but if there is ANY hesitation when warmed up with a quick turn of the throttle then move the clip down to the fifth groove.
Mixture screw one turn.

 Standard notice:
If forum members do not like my suggestions then move onto the next suggestion and do not call me names.



« Last Edit: July 11, 2013, 10:32:54 PM by lucky »
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Offline oldk6guy

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Re: carb gurus need your help
« Reply #10 on: July 12, 2013, 03:57:47 PM »
4 straight pipes. No baffles.
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76 cb750 k6: 4 into 4 exhaust, open air horns on carbs.

Offline oldk6guy

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Re: carb gurus need your help
« Reply #11 on: July 15, 2013, 08:06:51 AM »
is there any difference between 657B & 086A. i checked a chart that said they were identical but i have a hard time believing that.
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