ePREVIEW
1991 Yamaha YZI25, 250 and WR250Z
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YZ250: The 1991 Yamaha YZ250
features many engines changes,
such as a longer stroke top-end, 3.8
more cubic centimeters in the
cylinder, new porting, an ultra-hard
ceramic composit-coated cylinder
liner, more cylinder head vo lume, a
stronger piston and aluminum,
rather than steel, clutch plates.
Chassis-wise, the YZ250 has an allnew rear shock, a larger extruded
Deltabox swingarm, redesigned rear
suspension linkages and slightly
more rear wheel travel. Up front,
the inverted fork is 2mm larger in
diameter and has redesigned valving. Other changes include fewer
slots cut into the rear disc rotor to
help reduce pad wear, new pad
material, a new exhaust pipe, a
larger aluminum silencer, longer
side panels to help preven t the ri der's boot from wearing on the seat,
and reshaped rear fenders and side
panels. All the 1991 YIs have new
color schemes. The primary color is
still white, but the seat cover and
graphics are now magenta instead
of red.
YZ125: Similar changes have been
made to the YZI25 as compared to
the 250. It also has radically altered
engine porting, such as a larger and
rectangular-shaped exhaust port
and larger power-valve ports,
slightly more cylinder head volume
(0.5cc), an Alumite coating on the
flat-top piston, a larger clutch and a
redesigned power-valve system
(YPVS). The YPVS has an all-new
valve shape, and the governor is
also redesigned with two stepped
faces on its inner surface to provide
valve opening within two separate
ranges. The first step opens the
valve between 8000 and 9000 rpm,
and the second step opens the val ve
further between 10,500 rpm and
11,000 rpm. Like the 250, the YZI25
also has an all-new rear shock,
larger swingarm, linkage changes,
sligh tl y more rear wheel travel and
bigger forks .
WR250Z: Back for the third year in
a row is the Yamaha WR250Z cross
country model. The WR features
. the exact same changes as the motocross model but has some differences making it more suitable for
cross country racing. It still features
a five-speed wide-ratio transmission, a heavier flywheel and an 18inch rear wheel , unlike the 17-inch
rear wheels that come on the YIs.
The most obvious difference
between the YZ and the WR is
color. While the YIs are now white
with magenta, the WR is white with
turquoise.
