In reply to carrot_boy (North East Wales MC): mine is a different msr and old, so this might not help, but have you checked if the fuel line is clean, and if the jet is blocked? I think mine has a wire in the fuel line which can be pulled out to clean it? Like I said its not the same model, so I don't know if yours does? I seem to remember that shaking the jet and prodding it with the needle it came with cleared it if its the jet.