problems with McCulloch strimmer
 

My strimmer carburettor keeps slipping and causing the engine to "choke up" (according to my lad). As the repairmen in my area keep going bankrupt and as a true Yorkshireman, taking it to be repaired week in week out rankles a bit. I am led to believe is a quite simple adjustment but I know nowt abart engines. Can anyone point me in the right direction please?