Cold starting the Maestro after several weeks of hibernation was very hard. It seemed the float chamber, filter, pump and the fuel lines were completely empty and it took a very long time to pump up enough fuel to start the engine. After this daily or even weekly restarts are without any problem, so replicating the problem was difficult. 
It could be that the return valve on the fuel pump was not working correctly. So I replaced the fuel pump with another. I noticed the pump can be disassembled, so there might be scope for a rebuild.
