Got an old (?) weedeater rider from a neighbor. Doesn't start. Battery charged. No sounds when turning ignition key. Lights don't come on. Can start it by shorting posts on whatever it is that some ignition wires run in to though. Sorry, don't know what it is. Replace ignition switch?

Hi,
That is not your model number, it is the Home Depot SKU. The model number is many more digits long and probably starts with "HD" and is beneath the seat.
First guess is the solenoid, that thing you are shorting across. Be sure to disconnect the negative battery lead first. Also, be sure that if there is a smaller wire connected to one of those terminals (the battery one) that it is put to the same terminal with the wire it goes with. Solenoids can be connected either way except that wires that go together need to stay together.
Peace,
Clarke