how to fix my lawn mower?

Check the ground to the engine block. Make sure its clean and shiny. Make sure you've leaned the battery terminals really well. It sounds like a grounding problem for sure.

louis
July 2009

Assuming the click is coming from the solenoid (put your hand on the thing and you'll feel the click) that only tells us that the relay side of it is working, and we can't guarantee that connection is being made between the two thick battery to starter wires. So (carefully) bridge the large solenoid terminals - but be prepared for a spark. Does the starter spin? If so, replace the solenoid. If it doesn't, then either the starter itself is goosed or the battery or connections are poor. Check for any missing or loose thin wires going to the solenoid, too.

John
July 2009