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This may be a completely stupid question, but where to you attach the vacuum hoses from the motion pro syncpro tool? I don't see a vacuum screw or spot to attach. It's not the "vent" lines is it?
Also I just rebuilt my carbs with all new parts jets, gaskets, etc... and it is idling super high, but if I unscrew the idle knob to reduce this problem it dies at idle. Any ideas?
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Administrator
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What year is your bike?
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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It's a 1981 CB750K DOHC Keihin Carbs.
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Administrator
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OK. On your engine there are some screws on the top of the head, right in front of the rubber boots that the crabs attach to. Remove them, and attach the rods there.
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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Tools1, you are awesome thank you! I only have two adapter rods. Do I sync two carbs at a time and what do I do with the other two hoses? It says there is no need to plug them, is this true? Also I noticed that some forums say to sync two carb together at a time such as: 1,3 and 2,4 and then 2,3 together.
One more question. How far should my pilot (idol) screws be set in. On the PDF carb rebuil I have it says to screw in all the way until I get resistance and the back out 3 turns. IS THIS WHY my bike is idling so high?
Thanks for all your help!!
Wade
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Administrator
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I set the fuel screws by turning them in until the idle goes down. Then back them out until the idle stops increasing. I then turn them in to where the idle was the highest. After that I adjust the idle with the main adjustment screw/knob. As, for syncing the carbs. Since, you only have two rods, you are only going to be able to sync one at a time. Hook one up to carb #2, and then hook the other to one carb at a time, and sync all to the #2 carb. If after syncing the idle is high again, adjust the main screw/knob again.
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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Okay, I don't quite understand the fuel screw adjusting being that I would want to set it at its highest point. Where do I want to have the main idle adjustment knob set at first? All the way out providing less idle? If I do this then I can't adjust the idle down, only up. So I would think I would want to have the main idol know set in a middle position and dial the fuel screws so the idle is about where I want it permanently and adjust the main knob up or down after that?
Sorry for all the questions, just want to make sure!
Wade
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Administrator
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The idle mixture screw is what Tools was talking about when he said to shoot for the highest obtainable idle. That adjustment is for the air/fuel ratio at idle.
The idle speed screw,just set your idle to about 1200 rpm to start with. It'll change up and down as you start synching the them.You will probably have to adjust it a few times til your done.
Actual idle speed is really not important. The important thing is that all your vacuum readings match your #2 carb. That carb is factory set and non-adjustable.
Dont forget to keep the motor from getting too hot while you do this. A box fan blowing on the motor from the front will be fine.
Need anything else?Always feel free to ask.
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Administrator
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It is possible to sync all 4 carbs with just two gauges. Since units 1 and 2 are paired, and the same with 3 and 4, here's how you do it:
Connect your brass pipes to carbs 3 and 4. Use the appropriate screws to balance them.
Then connect the pipes to 1 and 2, and balance those two.
Then connect between 2 and 3, and use the bank adjustments to balance both pairs. The FSM is very helpful when locating which screws do what.
I hope this helps. Keep in touch, let us know how it goes, youtube is your friend, and good luck.
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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ShinyRibs,
I guess my real issue before I sink these carbs is that after the bike warms up, it idles SUPER high at like 3000 rpm when I roll up to a stop sign. When I adjust the main Idle knob down, I have to adjust it off enough that it eventually dies so I'm completely shutting the butterflies at this point I assume because the idle knob is not touching the throttle body to open them.
I should point out that I purchased the bike with pod filters installed will this mean that I have to screw "In" the air/fuel mixture screws more because of the increase air intake with these filters?
When I rebuilt the carbs, the kit came with 68 primary and 102 secondary jets. The ones that I replaced were 75 primary and 115 secondary. Could that have to do with my idle issue? It WAS doing it also before I replaced them.
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Administrator
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Those are pretty lean, for pods. However the idle issue sounds like a vacuum leak.
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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Administrator
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Those jets do sound awfully small,but I only have experience with the earlier carburetors. Not sure how mugh they differ on jet size. Do you have the CV carbs or the keyholes? Lucky has a good tuning guide for keyholes.It should get you in the ballpark,or even dead on.
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Thanks guys, I ended up taking the carbs off tonight after taking it for a spin. It seemed that screwing in the fuel/air mix screws sort of helped. I may need to go in a bit further but had to order a #4 outside carb because the one I have is cross threaded from the guy who owned it before and it broke off the little tip at the end of the mixer screw. I have one on the way and a couple more mixing screws.
Where would I look for the vacuum leak? Is it only at the screws where I plug the sync brass tubes into or are there other vacuum areas I need to address?
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Administrator
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cdaiscool on the forum here is giving away a set of carb bodies. Any way spray carb cleaner aroung the rubber boots that go between the carbs, and the head. If the idle picks up while doing this, you have found your leak.
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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Hey Shiny!
Just sent you an email and thought I'd catch you online here.
Hope you're doing well brother! I thought you posted on one of my threads about a dude that had re-jetted his carbs for pods on the DOHC. Can you refer me again, or maybe it wasn't you that posted that? I couldn't find it again :(
Wade
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Administrator
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I got your email.Hope things are well with you as well.I'm not up on the DOHC carbs at all. You might have talked to Hellbilly or Seestheday. They know about them pretty well. I think you might have talked to Hellbilly,actually.
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