Get a pair of insulated pliers and pull the sparkplug lead off. Than check the cable at the carby end that is is still connected and see , if it shortens out to the body of the mower,when shut down.
Jooply, July 2011
The throttle cable has dislodged itself.
steev2000, January 2010
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I can answer this question...
Why can't turn my lawn mower off or increas or decreas power?