Take off the top cover and remove the air filter, separate the air filter and place it in hot soapy water, clean and place on a radiator or in direct sunlight to dry thoroughly.
Chech the electrical connections inside the top cover, they are in the immediate vicinity of the on / off switch.
Check the condition of the HT lead that runs to the spark plug.
Remove the spark plug clean and re-gap usually .5mm.
Check you are getting a spark by holding it against the cylinder and firing the saw, it should spark.
Drain the fuel from the tank and use a fresh mix as petrol will evaporate over time and leave a too rich mixture leading to starting problems!
Good Luck.
A.L.Bradshaw.
July 2006