Did you ever find out the problem with your fuel leaking? I am currently having the same problem with fuel pouring out of the pipe on the bottom of the manifold
There could be an internal leak through the gasket between the top and bottom of the carb. Is there an 'O' ring that seals around the venturi and bottom half of the carb? if there is make sure it hasn't been pinched or split.
I have a Weber carb fitted to my series 4 Rapier there is petrol coming out of the manifold drain every time i turn the engine off and it is running rich. I have changed the needle valve and checked the float in hot water checked and rechecked the float setting's changed all the jet's and even the choke's,fitted a fuel pressure regulator set at 3 lbs yet petrol still come's out of the manifold drain. Any body any idea's why it's doing this ?