General view of the fuel separator attached to a throttle cable bolt on the carb adapter:

Whilst some fuel may gather in the pipe between chamber and carb it can never rise higher than the top of the carb port, which is lower than the bottom of the chamber and the pipe leading down to the vacuum capsule is even higher than that. Whilst it is inevitable that fumes will be in the whole run of the pipe from dismantling my failed capsules it seems apparent that it has been liquid fuel lying in the capsule and perishing the diaphragm that has caused the failure.