2000 Yamaha YFM400FWA(M) Factory Service workshop Manual, Page 346Get this manual
SIGNAL SYSTEM EB806024
2.If the neutral indicator light fails to come on: 1.Bulb and bulb socket
NO CONTINUITY
Check the bulb and bulb socket for continuityCONTINUITY Replace the bulb andor bulb socket
2.Neutral switch Refer to "SWITCH INSPECTION"CONTINUITY