L2_0_0_
S_Yc_o_m_o_ho_Y._
Z2_S_0_F
_
H
ad Yamaha just came out and
sa id, " He r e's our 2005
YZ250F; it's the same as last
year 's .. . enjoy, " we would
have been perfectly fine with
that . After all, what else could Yamaha do to
it to make it any better? The YZ, the bike
that won our 250F shootout last year (,04),
already had the best motor in its class and
did everything else - jump, turn , stop , start,
etc . - pretty darn good , too. Unfortunately
for Yamaha, though , the ' 0 4 Honda
CRF250Rand the Suzuki RM-Z250/Kawasaki
KX250F, the new kids on the block , d id
these things pretty darn good, too, which
prevented Yamaha from just sitting back and
resting on its laurels for another year. Instead
,Yamaha was forced to get back to work and
do anything it could to improve upon the
leader of the small-bore four-stroke class.
Of course, no bike can have too much
power, right? 50 Yamaha went to work on
the YZ250F's five-valve DOHC motor and
made some minor modifications to the
40th Anniversary
piston (with a new conve x dome), combustion chamber and intake ports. Yamaha also
wo rked on the entire air inta ke system,
which included redesigning the airbox that is
now similar to that of the YZ450F's filter
housing, and it revised the jetting and
readjusted the ignition's mapping.
These updates , Yamaha says, enhance
engine performance across the board.
Yamaha also went through the YZ250F's
chassis with a fine-toothed comb. Some of
the more notab le changes include both a
new tw in-chamber fo rk that better separates oil from air and also a ne w "transfer
co ntro l valve" that is said to im prove
middle- to full-stroke performance. In
addition , the fork tubes are held in place
by redesigned and stronger triple clamps
that also support brand-new aluminum
Renthal handlebars. ('Bout time !)
Since Honda 's patent on its front-brake
hose routing has finally expired, Yamaha
can now route its front-brake hose like
the Honda's - in a straighter a nd more
