Australasian Dirt Bike – May 2019

(Ron) #1

74 | MAY 2019 http://www.adbmag.com.au


TECH TALK I 2019 YAMAHA YZ250F


S rt


Tech Ed Mat boyd explains


what happened when Yamaha


added smartphone tuning


to its MX2 WEAPON


WORDS // MAT BOYD PHOTOS // JP MEDIA

y now you all
should know that
the Yamaha YZ250F
took the crown in
our 250cc Motocross
Shootout (ADB #474)
and when you read
that article (you
did, didn’t you?) you
would have seen us all banging on
about the raw power of the thing.
The YZ250F was already quite an
impressive package but, for this year,
Yamaha handed down some of the
latest features from the 450F such as the
electric starter, redesigned frame and
smartphone engine tuning. This bike
has been given the full overhaul, with
even the blue-anodised Excel rims put
on a diet to help offset the weight of the
electric starter.
The weight savings extend to the
plastics, shock, fuel tank (smaller),
handlebar, chain and swingarm. The
bike also received more top-end power,
a stiffer frame and stiffer fork and shock
springs to make this bike a real race-
ready package.
The smartphone app is free to
download and allows the rider to tune
the bike to suit their own preferences as
well as having the ability to log data
and give you service notifications.

Buyers save themselves over $400 by
not having to buy the plug-in GYTR
Power Tuner that was sold separately
for previous models. Everything the
Power Tuner could do can now be done
with the app that connects your
smartphone to the bike’s ECU by wifi.
To start the 2019 bike you simply
press the cold-start button on the 44mm
throttle body and then press the starter
button. Once you close the throttle for
the first time the cold-start button is
released so you don’t need to go poking
around the rapidly-heating engine for it.
The engine features a higher
compression piston, smoother intake
port shape with higher flow, new valve
train, lighter crank, a switch from a
Keihin to a Mikuni throttle body (still
44mm) and revised ECU settings.
Yamaha has also strengthened the
clutch to handle the extra power.
It’s hard to get an accurate quote on
horsepower readings these days as each
dyno reading will tend to vary but I am
hearing consistently that the new YZ-F
is pulling above 40hp, with a solid 2hp
gain over the 2018 model and has a rev
ceiling of 14,000rpm.
A lot of work went into the frame to
increase rigidity. Former world
motocross runner-up Josh Coppins now
plays a large role in Yamaha’s off-road
Free download pdf