Symptoms you've described sound like overly lean mixture on the idle/deceleration circuit.
This would most likely be an air leak into the inlet manifold (which you have ruled out) or a blockage in the idle mixture port of the venturi - possibly stirred up when you worked on the carby.
However it could also be a very rich mixture at idle cause by the engine cut solenoid on the side of the carby. A lot of people think this is a fuel cut solenoid, but on early Patrols it kills the engine by flooding the inlet with fuel to stop "running on" detonation firing when the ignition is turned off.
When the power is applied, the solenoid should "click" and you should feel it also with your finger. If there is no click, check for power supply and continuity with a multimeter