Q: FIRST AND FOREMOST, IS THE 2015
YAMAHA YZ250F BETTER THAN THE 2014
A: Yes; however, the 2015 YZ250F is not
exceptionally better than last year’s model. The refinements to the overall package have raised the bike to a
new level, and these minor improvements can be felt
by a sensitive rider. And, even the most maladroit will
appreciate that accessing the air filter no longer requires
the skill set of a safe-cracker.
Q: HOW MANY CHANGES WERE MADE TO
THE 2015 YAMAHA YZ250F?
A: We didn’t expect any changes, given that the
YZ250F was new from the ground up in 2014. But,
Yamaha targeted durability, rider comfort, engine
performance and showroom appeal.
(1) Engine. The YZ250F engine is different from any
other 250 four-stroke. It is the only down-draft, front-intake, rear-exhaust, symmetrical-port, canted-rearward
engine in the class. Yamaha believes wholeheartedly
that its engine layout is more efficient at filling and scavenging the combustion chamber. And why argue? The
YZ250F’s four-valve engine produces excellent horsepower at midrange, along with aggressive torque down low.
Yamaha upped the ante in 2015 with slight updates
to the engine platform. A new exhaust cam moves
the decompression pin by 6 degrees to reduce kicking
pressure for easier starting (though we never encountered any starting issues on the previous model). The
exhaust valve’s stem ends have an updated surface treatment to reduce wear and long-term clearance changes.
Additionally, the piston’s ring land has been reconfigured
to reduce oil consumption while improving lubrication.
As for the transmission, the gear stopper lever has been
changed to a solid, positive, roller-type design.
( 2) ECU. Yamaha recalibrated the fuel injection and
ignition timing to provide more control at low rpm. There
is also broader midrange torque and smoother over-rev.
A lighter throttle return spring creates 20 percent easier
( 3) Airbox. Praise to Yamaha’s engineers, as they
addressed one of YZ-F riders’ biggest pet peeves. Quarter-turn Dzus fasteners have replaced the hex-head bolts used
on the airbox cover. Accessing the 2015 YZ250F filter is
a breeze and can be done in a fraction of the time it took
( 4) Suspension. Kayaba’s Speed Sensitive System
(SSS) suspension returns for 2015 and comes with revised
fork settings. Yamaha’s in-house test crew focused on
improving the balance and stability of the YZ250F. An
increase in high-speed rebound and compression
KTM 350SXF 2015 YZ250F
Something borrowed: Visually, the 2015 YZ250F doesn’t
appear all that different from the YZ450F. However, the
YZ250F is distinctly unique on the track. It’s a race
weapon designed for all skill levels.