when the string is pulled the motor is turning over but then dies?

When did it last run? If some time, then chances are the fuel may have gone off - drain out the old (turn the mower over to do this and be careful) and fill with fresh. Check the air filter is clean and fited correctly and that the leads are connected firmly to the spark plugs - twist them around a bit to clean up the connection. After this, then on the assumption that the fuel is reaching the cylinder (there is no isolating tap, or if there is then it's turned on) turn the throttle to slow and pull the string a few times to ensure that the carburettor isn't flooded. Then turn the throttle to choke and try again, returning the throttle to fast as soon as the engine catches. If no joy, suggest you contact a dealer as the problem may be deeper.

john
August 2010