Thanks Norm, Max:
I ended up taking the carb off (it appeared to be in very good condition) and hitting it with carb cleaner and fitted a new carb kit.
Started first go and runs well.
The thing I can't get my head around, is that when I returned the mower the first time it was running perfectly, yet a couple of days later it has this problem??
I'm kicking myself now that when it came back I didn't test it first with new fuel, before I done the carby just to see if it may have been old fuel he was using.
Anyway we will see how it goes this time.
Again many thanks.
