If this (1) works do the following (2)
(1) loosen petrol cap & start it up If it runs & runs then the fuel starve is caused by a vacuum.
(2)Try cleaning the holes in the petrol cap - carefull not to expand their size, as this will effect the carb setting. Use nylon fish line .check the paper in the cap isn't oiled - only if it is it will starve the fuel by forming a vacuum in the petrol tank.Clean oil off with meths then dry with kitchen towel.Replace & try.
Jerry the Fish
September 2008