Sorry, had to open some Easter baskets with a 4 yr old.
I would start with cleaning ground connections at battery and at frame. Make sure good, then do tests.
Put the test light wire on the battery negative and the probe on the small solenoid stud with the wire that comes from the switch. (stay away from actual switch for now)
When you turn the key to start, you should have light. (Always be prepared for things to suddenly start moving)
Assuming you have light, does the solenoid click? If no light, bad switch, hot wire to switch, battery, main hot cable or solenoid. If light and no click, connections or bad solenoid.
If you don't have light, move probe to wire at small stud if you have light, does it click? If no, probably bad ground, switch or solenoid, if yes, maybe bad starter, or solenoid.
If you still don't have light, move probe to big stud at solenoid that has wire from battery. With or without the key on, it should have light.
If no light, bad cable, battery, connection.
The reason why I said to stay away from switch; get to poking around in there and accidentally short hot to the terminal for the CDI and we are all sad... We can do many tests that tell us much without getting back in there.
Let us know what you find and get back to us.