Carb sync issues. any ideas

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Carb sync issues. any ideas

SECTION8
Ok so i got the carb sync all set up and turned her on and this is what I'm reading. #1,2,3 are all in the area showing intake manifold leak or late valve timing. The #4 is the only one that is reading different and it is showing late IGN timing. Advice?
Army Combat Vet (Iraq 2005-2006) 4th Infantry Div.
1981 Honda CB750k
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Re: Carb sync issues. any ideas

seestheday
Sorry, maybe I'm not understanding the question... are you trying to sync them and it's not working?

Sync screws are on the carbs, and ideally you use a special screwdriver that has a wrench attachment so you can turn the screw and the locking bolt independently.  #2 carb isn't adjustable, you sync the other carbs to it.

EDIT: have you done a compression test?  I just re-read your post and think I get the question now.  My sync gauges don't have indicators for late ign etc on them.
1981 CB750K with 900 cams
90K KM's, rebuilt head, rebuilt carbs, upgraded valve stem seals

My wife's recipe website that I'm trying to help promote: Strawberries for supper. Yes, I am a lucky man.

My cb750 video site
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Re: Carb sync issues. any ideas

SECTION8
I am trying to ask what is causing the one to be so far off. None of the screws to adjust are moving the needle on the gauge. Thats why I have the picture there. Maybe this requires someone to actually see the issue. never mind
Army Combat Vet (Iraq 2005-2006) 4th Infantry Div.
1981 Honda CB750k
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Re: Carb sync issues. any ideas

SECTION8
In reply to this post by SECTION8
Is where the needles are in the pic anywhere near where they are suppose to be...
Army Combat Vet (Iraq 2005-2006) 4th Infantry Div.
1981 Honda CB750k
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Re: Carb sync issues. any ideas

Piute

   Hey Section 8 there's some vids in here may help

http://honda-cb750-s.456789.n3.nabble.com/Carb-Sync-tool-59-00-Cycle-X-TECH-TIPS-also-being-added-td3963996.html

                                             HOW ABOUT a few VIDEO's
                                                             

                                http://www.youtube.com/watch?v=IpqCUE8aCCk

                                     There's plenty here,(I havn't watch all YET)
                            1977 CB750 F2 Super Sport
<LET THOSE WHO RIDE DECIDE><RIDE TO LIVE-LIVE FOR JESUS> 
Native American from central Cal,  Kickstand UP in S.W.Missouri,
                                       
 
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Re: Carb sync issues. any ideas

TOOLS1
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In reply to this post by SECTION8
I have not done the carbs on a DOHC yet, but on the SOHC they seem to run best at 9# vacuum. Don't pay any attention to the diagnosis of the engine on the gauges. What screws are, you adjusting? Several guys have tried turning the fuel screws, and that just does not work. You adjust the ones on the linkage between the carbs.
TOOLS
Life is not about the number of breaths, you take, but the moments that take your breath away.
I don't have an anger problem. I have an idiot problem. Hank Hill
Never confuse education for intelligence.
Happiness is a belt fed weapon.
I just can't imagine what could go wrong.
No fire? No explosions? So whats the point of your story?
Those who are too smart to engage in politics are punished by being governed by those who are dumber. ~Plato
It couldn't be done, but the darn fool didn't know it, and did it anyway.
We all got problems. Ksharp
I like vintage bikes because they take me away from the clutter of technology that I work with everyday and back to a simpler time of mechanical elegance and simplicity.. "ninadm"
Darkwing Duck: The worst part of public transportation is the Public.
"That is awesome shit there" Re-Run
"Fear nothing, attack everything" Eric Berry
" Oh, you read that on the internet? Clearly it IS a massive problem. Of course it CAN’t be normal operation."

1976 CB 750-A X 2
1977 CB 750-A X 4
1977 CB 750-K
1976 CB 750 F
1981 CB 750
1966 Kawasaki SG 250
1981 KZ 750 LTD
1973 CB 350
1979 CM 185 Twinstar
1982 Honda XL 80
South of Eden (Kansas City MO)
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Re: Carb sync issues. any ideas

shinyribs
Administrator
Tools is right,just shoot for even,dont worry about the ''symptoms'' on the gauges. Remember that your #2 carb is non-adjustable.Whatever #2 is,make the others match and you'll be good to go.

Also,did your sync kit come with little valves? If it did use them inline on the hoses going to the gauge kit and all of your needle bouncing will go away. The valves help to lessen the ''blows'' from the vacuum pulses and will smooth the needle action out til it is rock solid. They should be little black pieces with thumb screws on them.
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Re: Carb sync issues. any ideas

cdaiscool
What everyone else is saying too. The 'diagnosis' sections are not relative to motorcycles. I think the company that makes those got a helluva deal on those gauges, and goes with those. Just look at the vacuum reading, and go from there.
Turbos, Hondas, 4-bangers, what could go wrong?

Fuelly

Shiny: [...] Considering the weather you've had to put up with I'd say you get an Iron Butt award and a Frozen Nipple trophy to go along with it. First time I've ever posted the word nipple... it ends here.
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Re: Carb sync issues. any ideas

LukeM
Administrator
In reply to this post by shinyribs
Good advice. The little white restrictor valves do help stabilize the valves.  However, I would recommend you connect all 4 gauges to a single vacuum source, to make sure you have the same reading on all the gauges, and that the white valves (if you're using them) are set the same.

Rather than focusing on the inches of vacuum on each gauge, it's more important to make sure they all read as close to the same as you can get them.  It will be a compromise based on idle/part throttle/power band.

If you are within 5-10 degrees across the board at idle, and at about 2000-2500 rpm, I think you're in good shape.  Once you get them close to sync, you may have to adjust your idle down, as the balance will help the engine run better.  That's how I noticed my bike was getting better when I got them sync'd.

Luke M
Used to have a 1979 CB750L, sold it as a parts bike, now riding a slightly modified 1984 VT700C. Network/Field Engineer. Central OH, USA, Earth, Sol System, Milky Way Galaxy, Universe.
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Re: Carb sync issues. any ideas

Lucky 1
In reply to this post by SECTION8
See how the needles are bouncing.

You need to turn the adjusters and get the gauges dampened down and not wiggling.

If you cannot stop the needle on the gauge from wiggling
it can mean the valve guides are worn out.

Vacuum gauges should read about 10Mg vacuum.

Also never turn the mixture screws to sync carbs.
On a Roadstar Adventure.
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Re: Carb sync issues. any ideas

Lucky 1
In reply to this post by SECTION8
The instructions tell you that, that is a possibility and to send the gauge back.
On a Roadstar Adventure.
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Re: Carb sync issues. any ideas

Lucky 1
In reply to this post by SECTION8
A very fast way to figure this out.

Take #4 gauge hose and hook it to #1.
If the gauge, is the SAME then the gauge has
a defect.

IF you take #4 gauge and hook it to #1 and it is DIFFERENT
then you know it is that engine cylinder, NOT the gauge.
On a Roadstar Adventure.
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Re: Carb sync issues. any ideas

shinyribs
Administrator
FSM calls for 18-22 cm/hg on a SOHC. Do the DOHC's run that low of a vacuum signal?
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Re: Carb sync issues. any ideas

Lucky 1
Depends on the rpm.
On a Roadstar Adventure.
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Re: Carb sync issues. any ideas

Zx6rguy
In reply to this post by shinyribs
This post helped me so much, i used those small inserts inbetween the lines but didnt know they were used to slow down the needles. But i still have a problem, the needles are all about equal when i was syncing them but still in the red, i checked my valves and they were all fine......not sure what the problem is.
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Re: Carb sync issues. any ideas

TOOLS1
Administrator
Just ignore those other markings on the gauges. The only reading you need to worry about are the inches vacuum. You should be around 7 inches.
TOOLS
Life is not about the number of breaths, you take, but the moments that take your breath away.
I don't have an anger problem. I have an idiot problem. Hank Hill
Never confuse education for intelligence.
Happiness is a belt fed weapon.
I just can't imagine what could go wrong.
No fire? No explosions? So whats the point of your story?
Those who are too smart to engage in politics are punished by being governed by those who are dumber. ~Plato
It couldn't be done, but the darn fool didn't know it, and did it anyway.
We all got problems. Ksharp
I like vintage bikes because they take me away from the clutter of technology that I work with everyday and back to a simpler time of mechanical elegance and simplicity.. "ninadm"
Darkwing Duck: The worst part of public transportation is the Public.
"That is awesome shit there" Re-Run
"Fear nothing, attack everything" Eric Berry
" Oh, you read that on the internet? Clearly it IS a massive problem. Of course it CAN’t be normal operation."

1976 CB 750-A X 2
1977 CB 750-A X 4
1977 CB 750-K
1976 CB 750 F
1981 CB 750
1966 Kawasaki SG 250
1981 KZ 750 LTD
1973 CB 350
1979 CM 185 Twinstar
1982 Honda XL 80
South of Eden (Kansas City MO)