Hi
It could be a couple of things 1st in the tank on the end of the fuel line is a filter this can block and can course fuel starvation second if the needles are set correctly the carburettor diaphragms could have gone hard and may need replacing as this governs the correct amount of fuel hope this is a help
Quince
www.swalelawnmowerandlandscapingservices.co.uk
quince
February 2008