[5th_bike]

What I understand from the wiring diagram, and to summarize what has been said before, is:

1) If the gear is in neutral and the side stand is down, the neutral switch provides a ground connection to the side stand relay and the neutral light, and ignition (starting/running) is possible.

2) If the gear is not in neutral and the side stand is up, the side stand switch provides a ground connection to the side stand relay, and ignition (starting/running) is possible.

Therefore, there must be something wrong with the connection between side stand relay and ground via your side stand wiring.

To test this wiring, put the bike in gear first, otherwise you will be going to ground via the neutral switch. Also (just for safety, may be superfluous) disconnect the battery's + (red) wire. Then, check the resistance between ground and the green wire that's going from the side stand relay to the side stand switch, at its connection at the side stand relay ( I hope that's possible, never did it...[yes it is, see 'edit' below]). Also check the connection ground - black/white wire from the side stand switch. The green and black/white wires also have a connector (shown on wiring diagram) that could be bad.

I would not know what the function of the diode in the side stand switch is other than making the 'ground' voltage for the side stand relay equal for both 'ground via neutral switch' and 'ground via side stand switch' Normal silicon diodes have a 0.6 V drop. Anyone else has an idea about the function of the diode in the side stand switch ?

Edit: (add-on) please refer to p. 192 of the service manual for the location of the side stand relay. Unplug the connector from the relay and check the wire that connects to pin "C" on the drawing of the side stand relay, p. 192. It should be green, according to the wiring diagram.
Since your bike runs fine when in neutral, the places where it could 'go wrong' are limited to 1) the connection to pin C inside the side stand relay (unlikely, but theoretically possible; if you have a diode tester, check if the connection pin C to pin A reads 0.6 V)
2) the wiring from pin C to ground, via the side stand switch.

Edit II: little correction