No polite way to say this: but, yes, it doesnt all add up .... what you are saying doesnt make sense.
Your statements about it should be "sending an earth signal to the soleniod" does not make any sence because that is not how it is suppose to work. (and the confusion not because because of calling it "earth" verses "negitive" verses "ground").
Is going to be difficult to determine what is abnormal, if you dont understand what is normal.
It will be hard to determine what is not working properly if you do not understand how it IS suppose to work.
I will repeat what I have stated before twice, but say it differently.
It is suppose to work this way:
Fuse puts power+ to the kill switch.
Then Kill switch puts power+ to the starter button (and the ignition).
Then Starter button puts power+ to the clutch swtich.
Then Clutch switch puts power+ to the solenoid.
The solenoid itself is mounted to the battery box which IS the ground-earth-negitive connection to the battery negitive (this requires that the battery box is in fact well grounded, which sometimes it is not and can be a problem, but not the problem you describe).
(I am assuming you have stock wiring. And if its not stock wiring, it is at least a negitive ground system.
Only positive ground system I have ever seen was on british & sweedisch & german cars from 50-60-70 years ago).
I think your bike had two problem that need to be investigated:
- why it draws high amps (heats up the wire, you say) but does not pull in the solenoid
and
- why the high amps doesnt blow the fuse.
Lets start with the high amps and solenoid not pulling in.
One way to troubleshoot a short circuit to ground (or other ecxessive high current) is to start at the intended load, the solenoid in this case, and dissconnect things one at a time, working your way back to the power source.
So, Disconnect the wire to the solenoid and hit the button (clutch swtich, ignition switch and all that) see if the high amps goes away, if it does go away it was the solenoid itself that was drawing all the amps.
If the amps dont go away, then you know it is something else along the way such as a short circuit to ground somewhere along the wiring or at one of the devices. So then go back to the clutch switch and disconnect that ... ... .... then maybe work your way to the starter button.
.
Forgetting any theory for the moment, if we take those three tests as good this is sounding more and more like a defective solenoid.
- If the screwdriver test drives the motor, the the primary cables are sufficent to run the starter motor.
- If the primary cable from the battery gets hot when activating the solenoid then the solenoid is shorting and is defective.
Is solenoid OEM or off of another application?