Here's simplified schematic showing just starter circuit. Note that clutch-switch plays key role in ground side of starter-relay. Needs either:
1. clutch lever out AND neutral-switch grounded (green on dash)
OR
2. clutch lever squeezed in
If clutch-switch is not plugged in, is defective or wiring corroded/broken, start circuit won't work. You want to measure for continuity to chassis-ground on Y/G wire between clutch-switch and starter-solenoid. It should be grounded when either #1 or #2 above is true.
As quick test to confirm power side of starter circuit is OK, you can short big power-terminals on starter-solenoid with some needle-nose pliers (be sure bike is in neutral 1st). Starter should spin engine just fine. Shows issue is with the control side of circuit. Most likely clutch switch or its wiring.
