There's one thing that scares me about this restart problem, which is, finding myself in a dangerous situation on the road when the engine has accidentally stopped and it needs to be restarted ASAP. So yesterday I took some time to get this thing sorted.
Apparently there is a clutch diode located somewhere along the wiring under the tank cover (picture attached - not sure if you guys are referring to it as the 'clutch switch'). It is taped to the wiring loom and a bit hard to see at the beginning. I removed the tape, removed the clutch diode, cleaned the contacts and put the diode back on.
Works perfect now. Fires up when in gear every time without hesitation.
Now I don't know exactly how this diode works (because it's got 3 pins instead of 2
), but my theory is that it ended up operating in the opposite way to what it should have done, that's why it it was sending current to the clutch switch (the one under the gear lever) when the bike was in Neutral, not in gear.