MGB - SU carb dumping fuel

[MSHolme13]

Hi all.
The back SU carb on my '78 BGT is pouring fuel out of the overflow pipe. Literally gushing out. The car as been off the road for over 12 months awaiting a new distributor, which I fitted yesterday. It started fine and ran OK for a few seconds, then became very lumpy as if misfiring and the fuel squirted out.

I'm not too hot on this, but this is something to do with the float chamber, correct?
What do I need to do?

Thanks for any help.

[MSHolme13]

Do I need a new part, or can I just 'un-stick' it??
Looks like it's carbs out as it's the later SU with the float chamber at the bottom??

[MSHolme13]

Great, thanks. I'll take it out and have a look...

[MSHolme13]

Just took off the carbs and the floats have fuel in. I assume there shouldn't be ANY fuel in them??