Releasing the handle will do one of two things depending on the set-up. It will either restrict the flywheel causing the motor to stop, or it will break the electric circuit causing the mower to lose spark. Once you figure which one it is doing then you can begin to trouble shoot. If it is the one that breaks the circuit, then trace the kill wire and see if it is dirty, corroded or not making the connection that it is suppose to.
cholbach, September 2005