We've got an oldish riding lawnmower we bought along with our new house from previous owners. It started up and worked a couple of times but now won't start. It just buzzes. None of the videos I can find online reproduce this sound so not sure what might be wrong.
Here's a video of it not starting https://youtu.be/-KvItIj6Hlo
Its your starter, more precisely, the starter mechanism (clutch/bearing) is not engaging the engine. It can be misaligned, broken teeth, foreign debris stuck in the mechanism, or just dirty and needs cleaning/grease.
Here's a quick youtube so you can hear it per request: https://www.youtube.com/watch?v=1trcMQFvvWU
There are a ton of videos on this topic out there, but once you inspect the bearing it should give you an idea of the issue.
Here's some more detail on it: https://www.youtube.com/watch?v=RhdSq4WOaDM
The battery sounds ok, however you should always check that first. Auto parts houses will test them under load. Second, the solenoid does not sound like it is driving the mesh gear into the fly wheel. Consider a new starter.
