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1981 CB750C bowls pouring fuel

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LikeItFast

1981 CB750C bowls pouring fuel

I know this is a common problem and I have done my research so far but nothing I have tried is fixing the problem. The bike is a new purchase and had some serious electrical issues due to someone doing a half ass cafe/bobber job on it. When purchased it ran like crap, but it ran. New plugs, wires and starter clutch and she ran much better. Time for a ride. On the first ride it ran crappy for the first 20min or so then started running great. About 30min later it started running worse than before. I came up to a stop light and smelled fuel. When I looked down not only was fuel coming out of the overflow on the bowls but it was pouring out of the back of the carbs. Got home and pulled the carbs. Removed the bowls to find the carbs were recently rebuilt with larger jets (scary). I'm assuming this is due to the fact that it has cone filters on it and Mac 4-1 exhaust. I polished the valve seats and replaced the float valves for good measure. I also measured the floats at 15mm. It's still leaking. Is there anything I'm missing? Any help will be greatly appreciated.

TOOLS1

Re: 1981 CB750C bowls pouring fuel

Administrator

Needles bad, floats bad, bowel vents plugged. Obviously the needles/floats are not shutting the fuel off like they are supposed to.
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)

LikeItFast

Re: 1981 CB750C bowls pouring fuel

Bowl vents? Where are these located?

LikeItFast

Re: 1981 CB750C bowls pouring fuel

I verified the floats float and the needles are new.

TOOLS1

Re: 1981 CB750C bowls pouring fuel

Administrator

Just because the needles are new does not mean they are sealing. You might need to raise your floats. And polish the tips, and seats again. The bowel vents are the tubes that come out the top/side of the carb bodies.
TOOLS

LikeItFast

Re: 1981 CB750C bowls pouring fuel

I'll try that. Should the needles have a rubber tip or be all brass. These came in an eBay kit so I'm not even sure if there the right ones.

On Jun 12, 2017 9:29 AM, "TOOLS1 [via Vintage and Classic Honda's]" <[hidden email]> wrote:

Just because the needles are new does not mean they are sealing. You might need to raise your floats. And polish the tips, and seats again. The bowel vents are the tubes that come out the top/side of the carb bodies.
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

Re: 1981 CB750C bowls pouring fuel

Administrator

They could be either, depends on the supplier. Be very careful of aftermarket kits. I have had problems with them. I try to reuse all the brass parts in carbs, and only order gaskets/seals from OEM sources just replacing what is needed.
TOOLS