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Leaking Carbs

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Leaking Carbs

rsercb
Is there a cure for leaking carbs ?  I am working on a 1974 Honda 750K
The float needles have been replaced and the carbs still tend to leak into the overflow tubes.
Sometimes the floats get stuck down and the fuel flows out the intake of the carb and into the air box.
Like I said the float needles/shut off valves have been replaced. Are there upgrade floats and shut off valves available ?
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Re: Leaking Carbs

Re-run
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If this happens a lot, you might have cracks in your floats. I would take them out and float them in some gas and see if they sink at all. While doing that, you replaced the needles but did you give the seats a good cleaning? If not, no needle in the world will seal right.
The ride IS the adventure. The destination is just to get gas!
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Re: Leaking Carbs

woodsrider250-2
Good advise.  

I always lightly burnish the seat with some lapping compound on a q-tip.
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Re: Leaking Carbs

rsercb
Hey thats a good idea. thanks.  I was wondering if they make a rubber tipped valve for the 750's. I've seen rubber tipped valves on some of the dirtbikes I have worked on.
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Re: Leaking Carbs

waddellpc-3
In reply to this post by rsercb
Hi,
I've just removed the carb rack because I was having same problem - gas would just run right through the carb into the air box - I'm not sure how to diagnose which carb(s) is the problem. The bike was sitting for 7 years.
-  so wondering if anyone has some insight or can direct me to a 'how to' link I can look at for installing carb rebuild kit to solve this problem.  
2. in your experience, what are chances of problem being solved by just cleaning needles and seat and checking float levels w/o replacement kits....I've done this once before with an in-line 4 but only taking off float bowls and adjusting float levels on 1 carb.
3. where is best place to get a carb rebuild kit?
4.  also, any ideas on how to determine which carb(s) needs rebuild kit? all 4 to be safe? (bit expensive) or just be examining each on the bench will do it ?...
any feedback would be great. thanx.
Rob 78 cb750K
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Re: Leaking Carbs

woodsrider250-2
In reply to this post by rsercb
Indeed.  In the days of ethanol 'enriched' gas, this is probably a good thing though.
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Re: Leaking Carbs

rsercb
Not following you.  Are you saying.....yes you can get rubber tipped valves ? And is your concern that  ethynol may "attack" the rubber ?
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Re: Leaking Carbs

Re-run
Administrator
I haven't seen any new needles that are NOT rubber tipped. My originals were and the replacements were. But you still need to clean the seats.
The ride IS the adventure. The destination is just to get gas!
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Re: Leaking Carbs

rsercb
Thanks, I'll clean the seats and pursue getting some rubber tipped needle valves.
Any suggestions on a good source for Carb parts ?
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Re: Leaking Carbs

woodsrider250-2
http://z1enterprises.com/

Other places have them, but I like supporting the guys that specialize in keeping these old bikes alive.  Their prices are good.
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Re: Leaking Carbs

brcree
In reply to this post by rsercb
  Hey, my cb 750 6k did the same thing, I cleaned the fuek system and put in a inline fuel filter....seemed to do the trick!
In God We Trust!
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Re: Leaking Carbs

Chaps
My Dad's '77 K model was running like a champ- little misfiring unless under at least a little throttle or at 5k or above rpmwise - but has been pretty decent for about 3 years, until I used a pressure washer on it. Now unless the fuel switch is on "off" it will leak out of the #2 intake (not bowl or any exterior fuel vent/passage) and down the airbox and drip all out on the ground. what happend when I pressure washed it?? lol
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Re: Leaking Carbs

TOOLS1
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"what happend when I pressure washed it??"
You broke it. Welcome to the forum. I have no idea why it would drip from the no#2 carb. I would bet it is the fuel line, or petcock. Also it could be one of the O-rings, for the fuel line fittings.
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"

1976 CB 750-A X 2
1977 CB 750-A X 2
1977 CB 750-K X 2
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: Leaking Carbs

hc243102
Just rebuilt my carbs, same problem. Leaking from #1 and #2 drains. How would the fuel line or petcock affect this? I was using a dirt bikes gas tank to test the carbs.
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Re: Leaking Carbs

TOOLS1
Administrator
It wouldn't. Your floats are set too high.
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"

1976 CB 750-A X 2
1977 CB 750-A X 2
1977 CB 750-K X 2
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: Leaking Carbs

seestheday
In reply to this post by hc243102
hc234102 you don't have the year of your bike in your sig.

Different years have different carbs.  E.g. my 81 does not have adjustable floats so they can't be set too high, but they can definitely stick or not seat right.
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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