New Problem, Idles fine, but once I rev it gets stuck at 4000rpm

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New Problem, Idles fine, but once I rev it gets stuck at 4000rpm

moogly4321
Got the needles fixed. Polished the seats and bam! no more leak. Now a new problem.

1. I got the bike to idle nice around 1000rpm. However, once I rev the motor it will get stuck at 4000rpm. I am fully releasing the throttle but the rpms will not drop unless i turn off the bike. If I turn out the idle screw it won't idle at all. It just dies.

2. The choke basically does nothing. When the bike is cold if I choke it, it just won't start. I have to feather the throttle to keep it running at idle. I have not yet cleaned out the slow jets, so that is a possibilitiy but I'm not sure on the above issue.

Thanks in advance,

Mike
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Re: New Problem, Idles fine, but once I rev it gets stuck at 4000rpm

TOOLS1
Administrator
You have a vacuum leak. Check the rubber boots between the carbs, and head.
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: New Problem, Idles fine, but once I rev it gets stuck at 4000rpm

moogly4321
Where/how do I check this?

Thanks.
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Re: New Problem, Idles fine, but once I rev it gets stuck at 4000rpm

TOOLS1
Administrator
First are the boots soft, and pliable? Or are they hard, and cracked? Are the clamps tightening, or are they stretched? You can sometimes find a leak by spraying carb cleaner, or WD-40 around the rubber boots while the engine is idling. If the RPM changes, 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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Re: New Problem, Idles fine, but once I rev it gets stuck at 4000rpm

moogly4321
Boots are soft and pliable, no noticeable cracks or tears. I will check this out tomorrow and see if that's the culprit.

Thanks.
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Re: New Problem, Idles fine, but once I rev it gets stuck at 4000rpm

moogly4321
How tight should the clamps be? Tight to the turn or cranked all the way down?
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Re: New Problem, Idles fine, but once I rev it gets stuck at 4000rpm

TOOLS1
Administrator
Usually they will close up, and you can not tighten them any further. I often replace the with 5/16 inch wide hose clamps.
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: New Problem, Idles fine, but once I rev it gets stuck at 4000rpm

moogly4321
How many turns out should I turn the air screws? Could that be the reason for slow idle return and it getting stuck? I have them 1 3/4 turns out right now per the repair manual.
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Re: New Problem, Idles fine, but once I rev it gets stuck at 4000rpm

TOOLS1
Administrator
I doubt it, but you can find the information on all the settings in the factory service manual that can be downloaded for free from the manuals section at the top of the home page.
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: New Problem, Idles fine, but once I rev it gets stuck at 4000rpm

jsmits
In reply to this post by moogly4321
Hey Moogly,

Not sure what model you have but I have a '78 CB750 and the carbs are... temperamental. When the carbs are in sync with my engine, they sit in such a way that the slides do not always come back down. I've tried everything I can think of to remedy the problem, but basically, if I only pull the throttle up 15% or so, and do so gradually, the slides will stay up and the engine with continue to rev at around 4000. I can overcome it by doing a quick throttle gun and pushing down hard. As long as the throttle reaches 50% the slides come down fine.

When it gets stuck at 4000, try a quick gun and push the throttle back quickly to see if it overcomes it. If so, you likely have the same sticky slide problem I do.

First thing you should do is buy a new pull/push cables from Motion Pro. I've been meaning to get my pull working as the one I order is too short for the '78 but I'm likely ditching these and tuning up a new set of cr29s at the end of the season. My carbs are a mess. I had stripped out threads that I had to fix, and now i have leaking float bowl gaskets that I'm replacing this week lol. I've had just about enough.