Alan,
I find my McCulloch MT 320 notoriuosly hard to start after refuelling, especially if it's hot.  You have to press the fuel-priming bulb seriously hard to get fuel through (about 10 times) and start on half-choke. 
Where the hell are the answers on this website.  All I see are questions and adverts.... Hmmm?
                
 Colin Rees, Swansea, Wales. UK
                
 April 2007