M Carb problem

[weekendrancher]

I just rebuilt an M carb. It worked fine at first, then started leaking a stream of gas out of the very bottom of the fuel bowl. It will also try to start, but not run. Any ideas? the floats are NOT stuck.
I took it apart again and blew out the ports, etc.
 

[old]

Needles seat not tight enough in the carb body or the needle not seating as it should or some dirt etc in the needle seat keeping the float from being able to stop the flow of gas. Of course that is if the float is in fact good and not filling with gas
 

[Bob M]

For whatever reason the carb float needle valve is not closing when the bowl is filled.

Possibilities:
- Float level set too high
- Float rubbing on the side of the bowl (look for sloppy float hinge pivots)
- Gas-logged (sunken) float
- A bit of trash caught in the needle valve seat and a bad needle valve. (I've struggled with bad needles supplied with a couple different rebuild kits recently).
 

[Bill in IL]

I have been through this before too. Did you install the gasket under the new seat when you installed it? BTDT stupid I know but something to think about.

Other that that look inside your fuel tank... is it clean? I installed a cheap filter inline between the carb and the tank. It works much better at getting crud than the sediment bowl. The filter can cause its own problems of airlocking the fuel line if you run out of gas but the end result of a carb not leaking (once its cleaned again) is worth it.
 

[rustyfarmall]

[rustyfarmall]

[BigTone]

Same thing happened to mine, check where the needle sits on the float, there may be a slight dimple from years of work and the needle is not seating correctly. I put in a new float, adjusted it and it works great now. best of luck
 

[The Red]

Check the gasket between the two halves. Make sure it is not overhanging inside the carburetor which could hang up the float. Trim it.
 

[soybeanjoe]

I have run into that problem when using an aftermarket carb rebuild kit. Carb will either leak gas out the bottom of the bowl or won't have gas in the bowl. I've found that replacing the needle valve & seat with a CIH brand usually eliminates the problem. An old IH mechanic was the one that recommended using the CIH needle valve & seat.
 

[rustyfarmall]