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Just so you know I'm going to switch this to Q&A so that we could have more time to work out your problem. This will give me some time to look into your situation and be able to ask you some questions.
unit approx 18 months old
unit stored in garden summer house
Gary Where are you I have answered your questions but you have not replied
Gary, Thank you very much for your help. Tomorrow I will buy fuel line cleaner and do as you have instructed, hopefully it will prove successful