Author Topic: Leaking Fuel Issue  (Read 2435 times)

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Offline carjoe0220

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Leaking Fuel Issue
« on: May 27, 2013, 09:18:57 AM »
1st, please be patient with my lack of knowledge. I grew up in the age of fuel injection and have never done any carb work.

I winterized my back last year by putting a bit of seafoam in the tank, topped it off with fresh gas, started it up, shut the petcock off and ran it dry. Threw a maintainer on it and a cover and called it a season. Now this spring I turned the fuel back on it started up with very little hesitation. As I was letting it warm up I saw fuel on the ground. Here is the source. 



My guess based on reading here and 0 experience is something to do with the float being stuck and not stopping the bowl from filling up? If I turn the petcock off it runs fine with no leak.

Thanks in advance for any and all help. Discovered this when I was trying to go for a nice birthday first ride and am itching to get out on the road.

Offline mrrch

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Re: Leaking Fuel Issue
« Reply #1 on: May 27, 2013, 09:33:25 AM »
I just had the same leak between #1 and  #2 over the weekend.
Orings had dried up and started to leak. I replaced my orings with replacements from a generic oring kit.
my build

1977 CB750K WITH 1976 CB750F ENGINE

Offline phil71

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Re: Leaking Fuel Issue
« Reply #2 on: May 27, 2013, 09:52:52 AM »
there is a small chance that they'll swell up and seal again before long. Give it a minute before you pull the rack apart.

Offline flybox1

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Re: Leaking Fuel Issue
« Reply #3 on: May 27, 2013, 10:00:21 AM »
phil71, gas is not supposed to leak from there. Swelling orings will not fix the problem

 if gas is leaking out of that butterfly valve linkage, you have a bigger problem in your carbs to deal with...like a stuck float or a bad float valve. 
Bang on the carbs to see if the float releases. 
Question....why isn't fuel leaking out your overflow tubes instead?  Better pull the carbs to check forfuel supply line blockage and do a general cleaning. 
« Last Edit: May 27, 2013, 10:04:29 AM by flybox1 »
'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

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Offline carjoe0220

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Re: Leaking Fuel Issue
« Reply #4 on: May 27, 2013, 10:25:46 AM »
phil71, gas is not supposed to leak from there. Swelling orings will not fix the problem

 if gas is leaking out of that butterfly valve linkage, you have a bigger problem in your carbs to deal with...like a stuck float or a bad float valve. 
Bang on the carbs to see if the float releases. 
Question....why isn't fuel leaking out your overflow tubes instead?  Better pull the carbs to check forfuel supply line blockage and do a general cleaning.

Thanks everyone for the replies.

FlyBox, any good DIYs to reference? Or youtube breakdowns? Never pulled apart a carb before, but willing to give it a go!!

Offline Shane72

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Re: Leaking Fuel Issue
« Reply #5 on: May 27, 2013, 10:38:53 AM »
The o-rings on the tee-fittings need to be replaced, as mentioned above.  They might indeed re-swell up and stop the leak in time, but if they have cracks in them (likely), the short-term fix will not be sufficient long term.

Here is a thread on the subject from a forum search...http://forums.sohc4.net/index.php?topic=92641.0

I can't remember from where I got mine, but new o-rings will fix you right up.

These are the supply lines that join the carburetors, ensuring that each carburetor float bowl gets supplied from the main tank, regardless of how many lines feed fuel from the tank.  The actual float needles and seats are physically below these lines, so the float bowl overflow tubes are not involved with this leak in any way.  This problem will leak any time the fuel valve at the main tank is on.

The first post indicated that the fuel leak stopped once the petcock at the tank was shut--this is the main clue.

Here is one of many online videos on the subject, but you need to watch fast on this one:  https://www.youtube.com/watch?v=sF-zsy6wW9g

All the best,

Shane
« Last Edit: May 27, 2013, 08:06:17 PM by Shane72 »
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Offline mrrch

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Re: Leaking Fuel Issue
« Reply #6 on: May 27, 2013, 12:54:22 PM »
Because it is leaking at one of the outermost carbs it will be easier to repair.
Carb rack off obvously then working with carb #4 see below.
Remove top cap of and remove the phillips screw that holds the lift arm to the cross shaft.
Remove the aluminum brace with the 8 phillips head screws.
Remove the 10mm headed bolt from the brace on the other side and bend slightly for clearance.
Remove the choke plate 2 small phillips screws (check to see if they were staked on the backside).
Remove one end of hose that connects the accellerator pumps.
The carb should slide off then.

And while the carbs are off it might be wise to check/clean the jets,check float heights (i like using the clear fuel hose method with these PD carbs)
my build

1977 CB750K WITH 1976 CB750F ENGINE

Offline phil71

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Re: Leaking Fuel Issue
« Reply #7 on: May 27, 2013, 05:56:35 PM »
i stand by my earlier post. Flybox, thats not the butterfly shaft, or the vents.