Starter? Battery?

[JayJay]

I think “nothing” is the key here. If the horn and lights work that means there is at least some charge. Trying to start even on a partially discharged battery, if the starter is good you should hear at the least a hum and a click as the Bendix tries to engage. Hearing “nothing” would indicate to me a starter, or maybe starter switch (although those are pretty simple and reliable, unlike a modern solenoid) issue.

Having said that, checking the battery as Gary suggests is a lot easier than pulling the starter motor. At least if the battery checks out OK then you will have eliminated a possibility.

Do check all the terminals - battery x 2, frame connection, starter switch connection. You may have a high resistance causing this. Low amps will flow but high amps won’t.