My garbage dispossal won't work. When I flip the switch it makes a humming sound. I tried the fly wheel but it is turning just fine when I turn it manually. What else could be the problem? Could the motor just be burned out? Are there any other things I should try before buying a new one?

It is a possibility that he motor for it is burnt out. Maybe you could have s pro look at it before getting a new one. I don't know what the price difference would be.

If it spins when turned manually - and at the same time it hums when switch is flipped, then I think it is time to replace it. Most likely, the motor is gone...

How old is you G/D, and what Brand?

Milo nailed it!
Sounds like you have a motor winding that's burned out. TIP: If you can replace with the same brand and model you won't have to install the drain. Simply use the old drain assembly and the new unit will snap right in. good luck, Tom,