VOL. 53 ISSUE 7 FEBRUARY 23, 2016 P77
and should start hitting show-
room floors as we speak. We
just got ours, and we'll talk about
it very soon in an upcoming is-
sue.) Yes, the YZ450FX is, like
a motocross bike, 100 percent
pure race, specifically designed
for GNCC and grand prix-style
competition. Honda, Suzuki and
Kawasaki have no such animal(s)
in their war chests these days.
Again, there are several
notable differences between
the YZ450F and YZ450FX. The
most significant and perhaps
most welcomed is the addition
of push-button electric start-
ing, which required a redesign
of the left engine case and
left-side crankshaft, the addi-
tion of a battery, and a stronger
generator. Output is bumped up
significantly, from 95 watts to
160 watts, and flywheel inertia
has been increased two percent
to smooth out power delivery. To
reduce vibes, Yamaha says that
100 percent of the reciprocating
weight is now balanced by the
counter-balancer, whereas on
the YZ-F, it's 88 percent.
Another major difference is
the gearbox. Ideally, an addi-
tional sixth gear would've been
added, but since that's not
feasible Yamaha went to great
lengths finding the ideal blend
of internal (and external) gear
ratios for the FX's now wide-ratio
five-speed transmission. What
they came up with was a lower
first gear that would require a
14-tooth larger rear sprocket on
the YZ450F to get the same ef-
fect (both bikes are fitted with a
13-tooth countershaft sprocket;
48T in the rear for the YZ and
50T for the FX). Second gear
you'd need an eight-tooth larger
rear sprocket, and third gear a
two-tooth larger sprocket. Fourth
gear is about the same overall as
the YZ450F. Fifth gear, however,
you'd need a four-tooth smaller
rear sprocket on the YZ to get
the same effect as the FX. Ac-
cording to Yamaha, this is about
a 30 percent wider range than
the YZ.
Yamaha didn't forget about the
(Opposite) In general, the FX, like
the YZ, is narrow but gets a little
wide if you slide far forward on the
seat, then you'll feel the radiator
shrouds a bit. (Left) The FX started
out life as a YZ450F, but by the
time Yamaha's engineers got done
with it, the YZ450FX had grown
an electric starter and was given
a wide-ratio transmission, among
other off-road tidbits.
