I found out that the mower is only 4 years old. I asked a local mower repairer to find a carby for me but after a comprehensive search they came back to me and said there is not one in Australia. I found one on amazon in the USA. I do not believe anything on a mower is rocket science so I stripped the carby down as much as possible and cleaned it with carby spray in every orifice I could find. Put it back together and now it is running fine. So now if all go well, in a couple of weeks there will be at least one spare 4X90HU carby in Australia. Thank you for everyone's advice.
