Liquid-cooled, DOHC 4-valve, fuel-injected engine with the
same forward-positioned, straight intake, rear-inclined cylinder, and
rear-positioned exhaust layout as the YZ450F.
The 4-titanium-valve cylinder head is matched to a fuel injection
system that provides power at mid-to-high rpm. The fuel injection
system instantly adjusts the air/fuel mixtures depending on altitude
and temperature, for a hesitation-free engine that delivers no matter
The aluminum Bilateral Beam frame offers a superb rigidity
balance and provides unmatched lightweight handling.
The exhaust pipe has an innovative layout, circling the cylinder,
giving the exhaust pipe proper length for an excellent exhaust
pulse effect. At the same time, the exhaust pipe has three different
diameters throughout the exhaust tract, bringing out excellent power
characteristics. This layout allows the silencer behind the side panel,
making it closer to the middle of the bike for centralized mass for
The layout of the seat, fuel tank, air box, and wrap-around exhaust
system moves the bike’s mass towards the center for exceptional
handling. The front intake layout with large air filter element adds the
benefit of reduced air filter maintenance due to its positioning away
from dirt roost from the rear wheel.
Accessory GYTR® Power Tuner lets owners adjust air/fuel mixture
and ignition timing maps to match engine performance characteristics
to the rider and track conditions in a matter of seconds with the
push of a few buttons.
New for 2015:
New front fork settings offer greater performance in the mid-to-end stroke.
Quick-release quarter-turn Dzus® air box fasteners for tool-less access
to the air filter.
A liquid-cooled, DOHC 4-valve, fuel-injected engine with the same
forward-positioned straight intake, rear-inclined cylinder and rear-positioned
exhaust layout as the YZ450F. The engine, with its straight and
symmetrical intake and exhaust ports and compact, high-compression
combustion chamber, delivers outstanding engine character in the highspeed
The adjustable fuel injection system uses a 44mm throttle body fed by
a high-pressure battery-less electric fuel pump. This ensures optimum
fuel atomization and air/fuel calibration for excellent rideability in a
wide range of riding conditions. The system controls the volume of
fuel injected and the ignition timing based on engine rpm and throttle
opening, providing hesitation-free response and controllability.
Various detailed design measures are adopted to reduce horsepower loss.
The forged 2-ring piston is light weight and is cooled by an oil spray
jet. In addition, the compression ring is a single-ring design instead of
the conventional two ring. This piston and rings, along with the offset
cylinder configuration, reduce friction loss and contribute to quick
response. What’s more, the specs for the intake/exhaust ports, cam
profiles, ECU, carburized crank, optimized balance ratios for the crank
web, transmission, clutch design, and other features, all work together to
create the YZ250F’s outstanding engine character with power output in
the high-rpm range.
As with the YZ450F, an innovative exhaust pipe design is adopted
to increase mass centralization and improve power development
characteristics. This layout moves the rear end of the exhaust pipe
farther forward and enables a muffler position close to the center of the
mass. Adjustments are made in the pipe diameter in its various sections
resulting in excellent exhaust pulse effect that contributes to high rpm
The compact wet sump lubrication system with piston cooler spray jet
maintains excellent engine durability and eliminates the need for an oil
tank, which lowers engine weight. This creates a more compact engine
that contributes to mass centralization and unmatched handling.
The transmission and shift mechanisms reduce drive-force loss during
gear changes and produce smoother shift operations and surer shift
The aluminum muffler is positioned closer to the machine’s center of
gravity as it is almost completely hidden by the side number plate. The
layout contributes to centralized mass for a lightweight handling feeling.
The front suspension has proven KYB® air-oil separated forks with
stiffer fork springs, new valving and a new fork outer tube to improve
performance in the mid-to-end stroke and aid fork bottoming resistance.
The rear suspension also features settings optimized for ideal damping
characteristics to match the chassis dimensions.
The large diameter 22mm front axle and top triple clamp increases
rigidity for excellent handling and front end feel. The handlebar mounts
are rubber mounted to improve comfort and reduce handlebar vibration.
The air filter is positioned away from the rear wheel which means less
maintenance for the rider.
“In-mold graphics” technology is a method in which the graphics are
molded into the radiator shrouds for improved decal durability and
Riders have a choice of two color options: Team Yamaha Blue/ White or