Looking for some help my 73 240Z with round top SU carbs leaking fuel out of the carburetor throat. 

I guess I would lift the pistons and see if they drop down freely? That's what the needles are attached to and the needles seat into the nozzles which close off fuel flow.

 

 

Thanks the pistons move freely. Should I remove the round domes to see if anything is out of place?

That couldn't hurt I wouldn't think, just make sure the pistons maintain their free falling when you tighten down the domes.

Is this something that just began happening, has it not been a problem previously? You could take the handle of a screwdriver and lightly tap around the float chambers to un-stick the floats if they could be stuck. Another way is stick a small red tube off a WD-40 can down the the vent bungs and see if the floats feel "bouncy" or buoyant in the fuel. Your fuel pressure couldn't have increased in any way? Sorry I'm just guessing but it will start a bunch of others to add their thoughts. Good luck. Cliff

Thanks I'll check the float chambers.

The only two ways I know of for fuel to leak out the throats is the fuel bowls are over filling or the float levels are set too high.

Overfilling can be caused by too much fuel pressure or a stuck needle valve

 I'd pull the float chamber top and check the float valve for extraneous matter blocking it open or wear on the needle or seat faces.

21 minutes ago, Patcon said:

The only two ways I know of for fuel to leak out the throats is the fuel bowls are over filling or the float levels are set too high.

Overfilling can be caused by too much fuel pressure or a stuck needle valve

Good call Charles and Mark! They can be disassembled and cleaned too.

 

Edited December 30, 20222 yr by siteunseen

See how we flock together? Like blackbirds. 

Thanks for all the great info. When I try to remove the cover on the float chamber the top gets stuck under a section of the main body. Is there a way to remove that cover with the float still attached?

A picture would help

24 minutes ago, Halvernaz said:

Thanks for all the great info. When I try to remove the cover on the float chamber the top gets stuck under a section of the main body. Is there a way to remove that cover with the float still attached?

Yes, they are made kind of shaped like a circle but idents on the sides where the bolts/screws hold them in place. If you lift up and turn them where the narrow part barely clears the carb body it'll raise up. Just barely but it will.