Gas Leak Carb

[Karl]

Ok Guys need help with an annoying gas leak form the Carb.
Rebuild Zenith- totally original runs really well. But when running seems to leak a little gas - When you wipe your finger under the carb you get a small amount of oily gas on your finger from the base of carb ( on the two bolts under the carb) I have reset the float level and the gas level is spot on using my little length of clear tubing. The float valve appears to be ok and sealing well. I'm thinking maybe wrong height on main jet ? any thing else -Thanks Karl

[Fred K-OR]

Plug threads striped???? or plug not in tight???? Bad gasket???? Bowl face not flat??

[Karl]

Originally Posted by 1930 coupe

Remove the bottom half of the carb and dry it off. Place it where it will not tip over and get the top of it level, Fill it with gas to the correct level which is 5/8" from the top and watch around the jets for leaks.
Also too much choking when starting will cause gas to drip out the bottom.

Thanks good idea I will give it a go -Karl

[johnbuckley]

follow this link to previous discussion only last week., with complete list of causes of carb gas leaks http://www.fordbarn.com/forum/showthread.php?t=132708 Gravity (even in NZ's Southern hemisphere!) manifests all carb leaks as a drip or dampness at the base of the carb.

[Tom Endy]

Right next to the two hex bolts under the bottom casting is a small drain hole. It is most probable that the fuel you feel on the two hex bolts is coming out of that hole. The hole is there to drain any fuel that finds its way into the throat of the carburetor. The fuel can be in the throat for several reasons.

The float level is set too high and causes fuel to dribble over the top of either or both the main jet and cap jet.

the small gasket around both the main and cap jet could not be sealing off.

Another cause of fuel being on the two hex bolts is as someone suggested the drain plug under the main jet (one of the hex bolts) is stripped or the gasket is not sealing. The reason the drain plug is often found stripped is because people are misled thinking it is leaking when in fact the fuel is coming from the small drain hole, so they over-tighten the hex.

As someone suggested place the bottom casting on a level surface and fill the reservoir with fuel. Wipe the throat clean of fuel and monitor it for a period of time. If fuel is leaking from either the main or cap jet it will leak into the throat and out the drain hole. The test will also reveal if the leak is from the drain plug or a crack in the casting.

Most of the time when fuel is leaking from the drain hole it is because the float level is set too high.

Tom Endy

[Karl]

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Thanks Tom

I have done the fill with gas and observe thing and couldn't see any leakage of gas into throat I did replace the gasket between the top and bottom half of the carburettor- and so far so good. If it happens again I will recheck the float level but it seems to be ok currently Thanks again Karl

[Tom Endy]

Originally Posted by Karl

Thanks Tom

I have done the fill with gas and observe thing and couldn't see any leakage of gas into throat I did replace the gasket between the top and bottom half of the carburettor- and so far so good. If it happens again I will recheck the float level but it seems to be ok currently Thanks again Karl

If your lower casting checked out good with the static test the fault is likely the float valve. There are several things to consider. The float level setting is one, another is the action of the float. Many floats have been molested over the years by people bending the arm to adjust the level. This causes the float to not come up correctly and can off-set the valve. The float seat is another cause, it may not be shutting off correctly all the time. If you have a lot of rust in the gas tank, an occasional particle can wedge in the seat.

I have found that a new float and a new Viton tip float valve from Bratton's have cured most all float setting\leaking problems. The level should be set by adding or subtracting gaskets, never by molesting the float. In almost every case the new valve and float from Bratton's dialed in correctly with one gasket under the float. Also, the black gaskets from Bratton's seal off better than the orange ones most suppliers carry.

Tom Endy

[jm29henry]

I agree with 1930 coup I have never seen a carb that does not have some wetness on the bottom as long as you are not getting a puddle on the floor you are ok.

[Karl]

Thanks Guys
I think I have found the solution-It was the float level . When I checked it with my little plastic tube I found that it was set a little high . What I had done is I had used the bottom of the upper casting as my reference point rather than the top of the bowl. This put the float level to high by the thickness of the gasket. Wasn't much but enough to cause the problem. Its always the little things and generally something I've done wrong-Fortunately I'm married so I am immunised when it comes to be constantly in the wrong! Karl