Yamaha 25BMH 30HMH Factory Service Manual, Page 40Get this manual
GEN INFO
FEATURES AND BENEFITS
IGNITION TIMING IN NEUTRAL
As the throttle is opened while the shift in neutral, the Lever moves to the right until it touches the Armand ignition timing advance is stopped at the point "A"The Arm moves to the right or to the left when the shift is engaged, since it is interlocked with the shift leverThus, when the shift is engaged, the Lever does not touch the Arm at the point "A", allowing ignition timing advance to take place