I've got a few ideas, is the transmission neutral light working ?
If you pull the clutch lever in, does the starter work ?
With the fuel tank off, do any of the relays click when the starter button is depressed ?
The starter relay if you can identify it, is one of the taller plastic cased relays, that should have what looks like a wiring diagram molded into the top of the case, if you can identify it, press down on the top of the relay, you can manually close the contacts in the relay by doing this and cause the starter to operate .