1.) Yamaha built the die-cast aluminum
cases to be compact and narrow with
good clearance. There are no plastic
shields of covers on the outside of the
2.) This photo of the left main casting
is oriented the same as the last photo.
The tiny shaft and gear closest to the
circuit board is the motor shaft.
The tiny gear turns the larger
gear on the lower right with
a smaller gear rising above
the surface of the gear. The
gears set in the casing are
the primary gear reduction
for the electric motor, and the
small gear sticking up is part of
the secondary reduction.
3.) This is the right-side main case
half. With the case oriented this direction, the bearing at the bottom supports the other end of the main shaft
of the electric motor.
4.) Here the gears have been
replaced in the case, including the
large gear that is the other half of the
secondary reduction. The square shaft and
the splined collar are normally outside the
case to attach the sprockets and crankarm.
5.) This is the same case as the last photo
with the removable white gear and electronic
6.) Yamaha’s service center at Currie Technologies
didn’t have a ;rm answer why, but this white gear replaces
the black one seen in the previous photo.