Carb Sync

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chewy999
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Carb Sync

#1

Post by chewy999 »

I'm sure this has been answered many times before, but can I ask couple of questions. Please answer as if you are explaining to a child, or an idiot, or me! :IDTS:

1. When you sync the carbs, what exactly are actually you doing?

2. Now I actually have the engine running, I notice that some of the exhausts are a lot hotter than the others. Will syncing the carbs sort that, or is there something else I should be doing before or after?

As usual, many thanks for any advice you can give me.

anim-cheers1 anim-cheers1 anim-cheers1

Just noticed I have put this in the wrong section :oops: perhaps a moderator can correct this please. Many thanks.
Previous Rides,
1980 CB250N Good to learn on
1981 CX500 good mid range tourer, went to Austria on it!
1983 GL1100C Pride and joy, sold when I bought my 1st house, big mistake
1985 GL650 Silverwing another mistake, horrible bike
1986 CBX550 Good commuter
1989 Suzuki GS750 (1976) cheap and cheerful until a dog ran out in front of me on Xmas Eve, 1991
Current bikes
2010 CB1300 back on a bike after 19 years, two divorces, children grown up etc
1980 GL1100 NOW ON THE ROAD, still use CB1300.
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sunnbobb
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Re: Carb Sync

#2

Post by sunnbobb »

Moved to the tech section.
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1978 Learning Experience
1980 County Road Hauler "Brain Damage"
1978 Cafe Custom Gl1000 "Vyper"
1977 Bulldog Inspired "Vaincre"
1981 Street Fighter GL1100 "No Quarter"
1983 Supercharged Street Drag "Anubis" (in worx)
1983 gl1100 mint restoration "Kristen"
1985 Aspencade..pondering.
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Re: Carb Sync

#3

Post by sunnbobb »

you are adjusting them so the butterflies open at exactly the same time, thus insuring the same amount of power is coming from each cylinder at the same time.
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---- Bradshaw Bikes custom polishing for your wing. Visit us on facebook!

1978 Learning Experience
1980 County Road Hauler "Brain Damage"
1978 Cafe Custom Gl1000 "Vyper"
1977 Bulldog Inspired "Vaincre"
1981 Street Fighter GL1100 "No Quarter"
1983 Supercharged Street Drag "Anubis" (in worx)
1983 gl1100 mint restoration "Kristen"
1985 Aspencade..pondering.
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Re: Carb Sync

#4

Post by sunnbobb »

Uneven temperatures can be caused by many things, including synch. First you need to synch the carbs, then check to see if the heat issue has equaled out. If not, them you need to adjust the mixture in each carb. Hot usually indicates a lean condition.
I found the end of the internet

---- Bradshaw Bikes custom polishing for your wing. Visit us on facebook!

1978 Learning Experience
1980 County Road Hauler "Brain Damage"
1978 Cafe Custom Gl1000 "Vyper"
1977 Bulldog Inspired "Vaincre"
1981 Street Fighter GL1100 "No Quarter"
1983 Supercharged Street Drag "Anubis" (in worx)
1983 gl1100 mint restoration "Kristen"
1985 Aspencade..pondering.
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chewy999
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Re: Carb Sync

#5

Post by chewy999 »

Thanks Sunnbobb for the simple answers and moving this to the correct section.

anim-cheers1 anim-cheers1 anim-cheers1
Previous Rides,
1980 CB250N Good to learn on
1981 CX500 good mid range tourer, went to Austria on it!
1983 GL1100C Pride and joy, sold when I bought my 1st house, big mistake
1985 GL650 Silverwing another mistake, horrible bike
1986 CBX550 Good commuter
1989 Suzuki GS750 (1976) cheap and cheerful until a dog ran out in front of me on Xmas Eve, 1991
Current bikes
2010 CB1300 back on a bike after 19 years, two divorces, children grown up etc
1980 GL1100 NOW ON THE ROAD, still use CB1300.
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jdvorchak
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Re: Carb Sync

#6

Post by jdvorchak »

The sync process can also uncover a problem. If one or more of the cylinders won't come up to the others, it could be a clogged or partially clogged slow (idle jet). Could also be a plugged or partially plugged idle mixture circuit. That is usually found by performing the "idle drop" mixture setting procedure.

Don't be discouraged. It takes years and hundreds of carbs to gain a high level of proficiency working with carbs. As you may have realized. There can be more that one thing, and possible more, that will cause the exact same symptom.

Take for example and colder pipe than the others as the symptom. Possible problems are:
Carb sync.
Idle jet plugged or partially plugged.
Mixture set incorrectly.
Mixture circuit plugged or partially plugged.
Float level.
Clogged or partially clogged float valve screen.
Bad spark plug
Bad spark plug boot
Bad spark plug wire
Bad coil.
Valve lash out of spec.
Ignition timing.

I'm sure you've heard the expression before and I'll repeat it here.. "Everything affects everything".
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Re: Carb Sync

#7

Post by miltoncaniff »

sunnbobb wrote:you are adjusting them so the butterflies open at exactly the same time, thus insuring the same amount of power is coming from each cylinder at the same time.
I am not claiming to be an expert, but my understanding is that you are adjusting for even vacuum air/fuel flow and actually adjusting the butterfly's to whatever makes the vacuum the same. This could mean the butterfly's are not opening at the same rate. This is to adjust for anomalies/dead spots in the carb bodies and intake ports. The reason people port their intakes is to smooth/remove those anomalies in the fuel/air mixture flow.

John
1977 GL1000/1976 GL1000
1975 GL1000/1975 GL1000 (Parts Bike)
2002 FLHRCI/1993 ZR750C3 Zephyr
1982 GS750EZ/1978 GS550
1978 KZ1000A2/1978 KZ1000A2 (frame only)
1980 KZ650F1/1979 KZ650B3
1979 KZ650C3/1981 KZ550A1
1977 KZ400A1 Deluxe/1979 KZ400B2
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ericheath
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Re: Carb Sync

#8

Post by ericheath »

It can also make up for a cylinder which has lower compression. If you have three cyl's at 150 and one at 140, they will pull unevenly despite a perfect bench sync.
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