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Author Topic: Carb Sync Spigots  (Read 1080 times)

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Offline slikwilli420

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Carb Sync Spigots
« on: June 24, 2011, 06:15:40 AM »
Was reading in the project section, and a gent over there drilled and tapped the carb insulator boots for 1/8" NPT brass fittings with barbs to hook up to the carb sync tool. Does anyone have a specific process and material list for this little project? Does this provide a more accurate reading of vacuum?
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Offline flybox1

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Re: Carb Sync Spigots
« Reply #1 on: June 24, 2011, 06:49:37 AM »
might not need to be done when sync ports might already be there..but we dont know what bike you have.
« Last Edit: June 24, 2011, 06:54:55 AM by flybox1 »
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Offline slikwilli420

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Re: Carb Sync Spigots
« Reply #2 on: June 26, 2011, 06:47:26 PM »
Sorry I didn't mention that. I have a '75 750 SuperSport. I saw a picture in another guys thread and it struck me as a way to get a better vacuum reading as opposed to the attachments on the carbs. Is this the case with this mod?
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Vintage Speed Parts Mashup: http://forums.sohc4.net/index.php?topic=133638.0
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Offline BobbyR

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Re: Carb Sync Spigots
« Reply #3 on: June 26, 2011, 07:40:27 PM »
Makes no sense actually. The synch ports on the carbs are closer to the vacuum source.
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Offline slikwilli420

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Re: Carb Sync Spigots
« Reply #4 on: June 27, 2011, 08:05:49 AM »
Isnt the vacuum source the motor itself? Then if they were moved from the carbs to the carb insulators they would be closer to the vacuum source and give more accurate readings, right?
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All you gotta do is do what you gotta do.

Vintage Speed Parts Mashup: http://forums.sohc4.net/index.php?topic=133638.0
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bollingball

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Re: Carb Sync Spigots
« Reply #5 on: June 27, 2011, 08:48:05 AM »
Makes no sence  ??? Lot of work for no gain. If you are that anal tap in next to  never mind now you have me doing it ;D ;D
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Offline BobbyR

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Re: Carb Sync Spigots
« Reply #6 on: June 27, 2011, 09:05:42 AM »
Quote from: slikwilli420 on June 27, 2011, 08:05:49 AM
Isnt the vacuum source the motor itself? Then if they were moved from the carbs to the carb insulators they would be closer to the vacuum source and give more accurate readings, right?

This is not the same exercise as using vacuum reading to diagnose an engine problem, so the carb ports are the perfect place to take a reading. It is about adjusting each carb so that all 4 pull the same vacuum.

On the 750 #2 carb is fixed and known as the reference carb. The other 3 carbs must be adjusted to pull the same vacuum as #2. If number 2 is pulling the lowest reading, the other carbs must be adjusted down to match it.


 
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Offline TwoTired

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Re: Carb Sync Spigots
« Reply #7 on: June 27, 2011, 09:46:22 AM »
If you use early CB550 carbs and late CB550 intake manifolds, you wind up with no vacuum ports.  To do a vacuum sync you MUST add a new port somewhere between carb slide and intake valve, in this case.
I don't see any technical advantage to adding more access ports than just the one for carb vacuum balancing.

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Offline slikwilli420

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Re: Carb Sync Spigots
« Reply #8 on: June 27, 2011, 12:16:28 PM »
Straight answer. Gotta love it. Thanks to all who replied to this inquiring mind.
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All you gotta do is do what you gotta do.

Vintage Speed Parts Mashup: http://forums.sohc4.net/index.php?topic=133638.0
Rickman CR Parts Kit Refresh: http://forums.sohc4.net/index.php/topic,154837.0.html
AHRMA CB750 Racer: http://forums.sohc4.net/index.php/topic,158461.0.html
AHRMA Superbike Heavyweight Racer: http://forums.sohc4.net/index.php/topic,173120.0.html
'76F CB750 Patina Redemption: http://forums.sohc4.net/index.php/topic,174871.0.html
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