Starting problem revisited

[crickleymal]

So the starting problem reoccurred today. I've had the valve clearances done and new carb inlet rubbers fitted. The symptoms are, it will start fine out of the garage in the morning. Then on subsequent starts it will fire and idle then over the next 20 seconds the revs will fall away and even blipping the throttle won't save it. It then takes up to half an hour to get restarted. Oddly enough when I try to restart it I have most success with no choke but blipping the throttle.

My car mechanic suggested water in the float bowls but I drained them this morning and they're ok. I took out a spark plug and it was dry.

Help please!