First findings while having a poke around under the tank of the newly acquired '30;

The bike is generally mint & unmolested

None of the plug caps were pushed home - just resting on the top of the plugs.....

Mice find the wiring loom tasty.....

The petrol tap doesn't shut off under atmospheric pressure.....
Upon disassembally, all is clean & diaphragms look fine. Reassemble & it shuts perfectly until vacuum is applied, the tap opens then it won't close again when vacuum is removed???
A closer look reveals what looks like a 1 way valve just inside where the vacuum spigot is - remove the small push fit housing & diaphragm & the tap works perfectly.
The 1 way valve prevents the vacuum side of the diaphragm from receiving atmospheric pressure when the vacuum is removed which prevents full closing of the fuel flow.

May help someone,
Comments???

Phil