Fuel leaking from carb

[benlawlor85]

Hi All,
Thanks for all your help on previous posts, but once again i have a little problem.
My right carb is leaking, so i thought just sticky float so took the bowl off and checked it.
and there is no problem there at all.
I am wondering tho could it be bowl is leaking next to the over-flow tube?
or a hole in the float?
any ideas of what to check first?
Or do i just buy an over-haul kit and hope that fixes it!?
keeping in mind the bike is used to commute! so cant be out of action for that long.
Thanks in advance
Ben

[donbmw]

Have you checked to see if fuel shuts off when you move the float up and down. The fuel level could be to hight.  You could have a pin hole in the fuel bowl.

Don

[Bob_Roller]

It could be a foam float that has absorbed fuel, and now is heavier than it should be, and won't get high enough to shut the needle valve off.

The foam material that the float is made from can be damaged by ethanol in the fuel, by damaged I mean it will absorb fuel, though it may not appear to be different than the float in the other carb.

If you take the carb bowl off again, the fuel should shut off when the arm on the float is about parallel to the surface of the carb body that the bowl sits against.

The needle valve that the float pushes on, has a rubber tip, and that may be old hardened and deformed as well, causing the fuel not to shut off.

There is a gasket that the float bowl seals against, it looks like a cork type material, check to see if is damaged.

[benlawlor85]

Thanks guys,
It is shutting off when the float is up!
which is why im thinking float or hole in bowl...?
will see if i can take float off 2m and see it it floats in some fuel!
thanks again
Ben

[Bob_Roller]

By chance does this only happen if you put the bike on the side stand, or does it happen all the time ?

[Justin B.]

It could be one (or combination of) several things:

1.  Float misadjusted.
2.  Deteriorated float.
3.  Trash intermittently causing float needle to not close.  Quite often from a fuel line crumbling on the inside.
4.  Hole in float bowl.

If this bike had sat for a long time #4 is a definate possibility.  One of the float bowls on the '82 LS I picked up had a couple of pin-holes.

[benlawlor85]

Hi,
and thank you all for advice etc,
just checked both bowls and floats, well as much as i could while still attached to bike.
Left one is fine and no leaking when fuel flowing
but the right one,
the bowl is fine no leaks but when attached to carb and fuel on it leaks slowly from the over-flow
so i have ordered a float!
Will keep u updated on progress
Cheers
Ben

[Bob_Roller]

Ben

I don't know how much knowledge you have on the Bing carbs, but the hinge pin that the float pivots on only goes on one way.

One end of the pin has serrations, and the aluminum post it goes through, has mating serrations.

Just be mindful of this during dis-assembly and re-assembly.

[benlawlor85]

Thanks for that bob,
Dont know much about Bings was always used to good old SUs on my MG.
I have ordered a new pin as a matter of course anyway and will keep it in mind that they go in/out one way
Thanks again
Ben

[Ed Miller]

Ben, are you getting your parts from the Bing Agency?  If so you may want to order their book on the carburetors, full of good stuff.

[benlawlor85]

Hi Ed got the float from Motorworks as had other parts on order too!
But bad news!

Installed the new float without taking the carb off the bike! but she is still leaking! so i dont know.
Think i will check bowl for leaks again!
then maybe the valve!?
are there any O-rings etc that can perish or does it have to be the valve?
The fuel line looks a bit crap so will buy a metre or so of that too and add in some in-line fuel filters too!
Cheers
Ben

[Frank_M]

Installing the float with the carb still attached may have prevented you from seeing if the float was closing on the valve needle. There's a tab on the float and when the float is level in the bowl, this tab should just be touching the valve enough so that the valve closes. If not, bend the tab a little.

[benlawlor85]

Hi Frank,
Just been reading the haynes manual in bed! how sad am i, and it mentions bending the tab! think that must be it as the needle defo closes the fuel off when i push the float up so the tab would explain it all!
Old float was probably ok!? ah well thats one less part to replace in the future!
Cheers
ben

[Justin B.]

Have you not checked the float adjustment? With the gas turned on the flow should shut off when the float is raised and parallel to the bottom of the carb body.  If not, then bend the tab.  If there is crap/granules in the seat from a deteriorated fuel line it will often keep the needle from seating all the way and nothing you do is going to make any difference UNTIL you remedy this problem.  

Remove carb, disconnect fuel line, turn upside down, remove float and needle, blast carb cleaner backwards through the valve opening and watch what kind of crap blows out.  After this put your needle and float back in and double-check the adjustment.  It is very rare for a seat to be worn out, the folks at Bing told me that the seats used with the rubber tipped needles will virtually last forever.

You should probably do this on both sides while your at it to save yourself the aggravation.

I only stress this because I went through the same thing - new needles, floats, adjustments, still leaked until I blew out the crap.  The cloth covered (or any rubber) fuel lines have a tendency to deteriorate internally and little crumbs of rubber flake off, get hard, and then play hell with the float operation.

[benlawlor85]

Cheers Justin,
Will do that on sunday i think!
Just need some carb cleaner.
should take about an hour to do both right?
Cheers
Ben