Dirt & Trail SEPTEMBER 2022

5% more power across the range and weighing just 109 kg with a
full tank of fuel.
All new YZ450F engine: Lighter, faster, easier.
For 2023 the YZ450F’s engine has undergone a total redesign,
with every component reviewed and analysed, making this the
most significant change to the powerplant since the original
reversed-head layout was introduced in 2010.
Lighter and more durable, they say the new engine is designed to
deliver more linear output characteristics for stronger and better
pulling power with improved driveability, making the 2023 model
easier to ride at all engine speeds.
New piston, lightweight cylinder and redesigned crank assembly
The reversed-head engine has an optimized combustion chamber
and a newly designed piston, as well as a lighter weight cylinder
body that enhance power output and behaviour. To accommodate
a 500rpm rev limit increase, the new engine is equipped with a
high-precision, low-friction cam chain – and for increased running
efficiency the crank assembly and con rod is redesigned, and a
lighter plain bearing replaces the previous needle roller design. A
new single balancer weight features a new hollow balancer shaft,
and this improved lighter design reduces vibration.
Increased air intake volume
For 2023 the intake design is further improved by a reshaped
intake port with a straighter passage to the cylinder head and the
use of larger diameter 39mm titanium intake valves that increase
air intake volume by 9% at maximum valve lift. To complement the
improved intake layout, the exhaust port’s shape is also revised to
give a smoother connection to the exhaust.
New air intake routing with vortex airbox
There is a completely new air intake path, with fresh air now
channelled through the space between the fuel tank, frame, seat
and sidepanels. This re-routed airflow helps to prevent water, dust
and mud from entering airbox, and results in a lighter and slimmer
machine with more compact bodywork.
The 2023 model is also fitted with a highly efficient airbox
design which creates a vortex so that dust is separated from the
incoming air by centrifugal forces before it enters the new round
three-dimensional filter.
Newly designed transmission and lightweight clutch
To match the engine’s 5% increase in overall power a newly
designed transmission is fitted. The distance between the drive
shafts has been widened and the diameter of each gear increased
to reduce weight and enhance the strength of the 5-speed
gearbox.
The previous model’s 2-piece steel/aluminium clutch is replaced
by a durable and lightweight one-piece steel design with disc
springs instead of conventional coil springs. They say that the
new clutch is significantly lighter and slimmer, weighing 0.75kg
less – and there’s a more direct feel and lighter pull at the lever.
Increased durability
For increased durability across the more powerful engine’s wider
rpm range, the new YZ450F engine is equipped with an updated
cooling system as well as a new dry sump lubrication system.
Redesigned aluminium bilateral beam frame
Yamaha’s engineers have focused on redesigning the aluminium
bilateral beam frame to provide a lighter feel, increased agility and
improved stability.
Ts&C