Fuel Leak

[HJF]

Here is a picture as they now come when new ...
That was my problem. Carbs were new but I fitted the cold start elimination kit which came with a new plate with no hole, so I fitted it. Noticed after putting the car away, a little time after they would be wet underneath at the rear. Carb to manifold was okay so realised it was seeping from the bottom of the plate. Put the original plate with hole back on and all okay. Have spoken to a few “specialists” about this and was surprised at lack of awareness.

[Mazzini]

Brilliant! Thank you!

Parts ordered.

[SENC]

Must be the most talked and debated problems with old Webers. Consensus being worn inner shaft bearing bore, shaft runs directly in body, and when worn allows the depression in the main venturi to create a vacuum in the closed chamber that houses the pump jet control rod. This pulls fuel from the pump jet piston cavity via the control rod into the closed chamber. It’s from the closing plate the fuel leak reaches the outside then runs along and accumulates and drips at the ‘ O ‘ ring flange.

Good call on this. I had heard about the vacuum-induced leaking potential and when rebuilding replaced my back covers with the newer ones that have the hole in them (readily available, Rob) but never got a great explanation for why this occurred.

Eric - thanks for pointing out your observation, I'll do so benchtop to get an idea. I have a couple glass straws that definitely displace fuel, but once I had the right level I'd planned to mark them for consistent checking - but if observing the level at the bottom of the idlejet well is just as good that is even simpler.

[Mazzini]

The closing plates and gaskets arrived. I fitted them and set the float heights using Eric's method. The first carb is now dry, but the second carb, which still has a slight float height issue, is not, I'll have another crack at it tomorrow.

Thanks for all your help.