Yamaha YZs
Aluminum frames and a five-speed gearbox
for the 450 highlight new YZ thumpers and even the two-strokes get some attention
By THE STAFF OF CYCLE NEWS
PHOTOS COURTESY OF YAMAHA
42
JULY 20,2005 •
CYCLE NEWS
s expected, the YZ-F four-strokes
got most of Yamaha's attention
for 2006. For all intents and purposes, the new '06 YZ250F and
>fZ450F are all-new motorcycles,
both getting new aluminum frames and pretty
much complete engine overhauls.
Besides the aluminum frame, one of the
biggest pieces of news concerning the 450 is
that it's going back to the five-speed transmission. It got a four-speed when it went from
the 426 to the 450 in 2003, but it was never
really a big hit for Yamaha, many feeling that
the four-speed hindered the bike's versatility
and performance on the track.
Both the yz 125 and 250 two-strokes and
the yz250 and 450F four-strokes share many
changes, including an all-new fork that features
a new speed-sensitive system that results in
increased low-speed and decreased highspeed damping control, which Yamaha promises greatly improves overall performance over
last year's fork, since it is now more sensitive
with the fork compressed. The new fork
shares only five parts over the previous fork.
In the back, all of the ~ get a new,
stronger swingarm and an all-new shock that
A
features a 2mm-larger-diameter rod (16mm
to 18mm), a new friction-reducing coating, a
30-percent-larger capacity reservoir and a 30percent-lighter titanium spring - a first,
Yamaha claims, for production motocrossers.
For improved feel, all the YZs get a fatter
front-brake lever, a larger and easier to operate clutch adjuster, adjustable handlebar positions and a new rear-brake caliper. They also
get a new seat that is 10mm taller and has
softer padding.
In the cosmetic department, all of the bikes
get a new front fender and front number plate.
The 250 and 450F share a few items, as
well. One, of course, is the aluminum frame
that is made out of nine different parts and
three different kinds of aluminum. One of
Yamaha's main objectives with the frame was
to lower the F's seat height and eG. Yamaha
says it managed to drop the height of the
frame by changing the steering pipe location,
the subframe mount and swingarm pivot position. To help achieve a lower seat height, the
Fs get a new subframe and, with it, a new airbox. Yamaha claims that the total seat height
of the Fs has been reduced 20mm.
Motorwise, both of the Fs get new radiators
