The 250 SX-F has been on top of the MX2 World Championship for many years now and adds a second AMA Supercross Lites Championship to its crowded trophy cabinet. But that’s no surprise. The successful combination of a powerful and torquey engine in a lightweight and agile chassis is bound to launch the 250 SX-F onto podium after podium.
The 250 SX-F engine is known to be the
strongest engine in the MX2 paddock. It
screams at the top of its lungs at 14,000rpm,
but is equally happy producing tons of torque
and power across the rest of the rev range. Its
compact architecture contributes to an
excellent mass centralization, supporting the
rideability of the bike. And it only weighs
26.1kg. That’s including the incredibly
beneficial electric starter. David, meet Goliath.
The centerpiece of the compact DOHC (double
overhead camshaft) engine is the cutting-edge
cylinder head. It features two overhead
camshafts, which activate the titanium valves
via super-light finger followers with a hard DLC
coating. New lateral brackets (now made of
aluminum instead of steel) allow an efficient
fixation of the engine to the frame and shave off
another couple of hundred grams.
The 250 SX-F has a rigid crankshaft, which
features a connecting rod with a plain big end
bearing featuring two force-fitted bearing shells
run directly on the crank pin. This design is a
major prerequisite for the extremely high
engine speed levels and the unrivaled
maximum power of the 250cm3 engine. Not
only that, it enhances the engine’s durability,
allowing long crankshaft service intervals, which
is a huge customer benefit in relation to time,
effort and cost.
The engine is fitted with a smooth 5-speed gearbox, which features a special surface
treatment on the 2nd, 3rd and 4th gears for best reliability. The advanced
´No Dirt´ gear lever design prevents dirt from blocking the joint of the lever
and guarantees a safe activation of the transmission. All 4-stroke engines are fitted with a
gear sensor to give the option of different engine characteristics for each gear.
The 250 SX-F is fitted with a unique electric
starter as standard, which is a clear advantage
when it comes to crunch time in the heat of
battle. A strong starter motor made by Mitsuba
and the proven starter drive will fire up your
track star time and time again at the push of a
ENGINE CASES AND COVERS
The design of the die-cast engine cases
minimizes weight and allows for a very
centralized shaft configuration. This makes the
engine short and compact, while contributing to
an efficient centralization of masses. The
engine covers also feature a solid surface
structure that reduces the wear caused by the
rider’s boots. Brilliant.
ENGINE MANAGEMENT SYSTEM
The state-of-the-art Keihin Engine
Management System with electronic fuel
injection features a 44mm throttle body. Thanks
to its unique injector position, the engine’s
response is instantaneous. And to make life
even easier, separate systems for cold starts
and idle adjustment await you. The lightweight
ECU features a unique traction and launch
control system for lightning-quick response
when the bar drops and maximized grip thanks
to different maps that sync with to the gear
you’re in. As an ultimate bonus, the rider can
unleash an even more powerful mapping via
the handlebar map switch.
CYLINDER AND PISTON
Inside the short cylinder, with a bore of 78mm,
thumps a box-type piston made by CP. Its
crown geometry is adapted perfectly to the
high-compression combustion chamber (14:1),
where its rigid structure and low weight shine.
Thanks to the low oscillating masses, the
engine is as cheerful as it’s strong.
COUNTER BALANCER SHAFT
In order to balance the mass-forces, the 250 SX-F engine uses a multifunctional
counter balance shaft, which at the same time drives the water pump
and timing chain. Win, win, win!
KTM’s proven cooling system routes the coolant from the cylinder head through
the frame triangle, directly to aluminum radiators made by WP. Due to
flow optimized internal circulation and CFD-calculated air ventilation,
the system is superbly efficient. In addition, well thought-out radiator guards integrated
in the front part of the spoilers provide protection in case of crashes.
The highly compact CSS clutch (coil spring
steel) features a wear-free steel basket fitted
with seven clutch plates, which are extremely
heat resistant due to their steel carrier discs.
The Brembo hydraulic system provides easy
and precise modulation.
The main target for the KTM engineers when developing the SX models was a massive
weight reduction compared to the previous generation. The result: the current
SX-F models are the slimmest, lightest bikes in the competition, even though the
4-strokes are equipped with an electric starter as a standard feature, while the
competition still needs to be kick started. You can just focus on kicking ass.
The airbox design offers maximum protection of the air filter against soiling,
while ensuring maximum airflow. The large twin-air filter is mounted in a
stiff cage, which at the same time holds the system in place. This design is so
simple, you could still pop a fresh one in with a face full of mud.
Without tools. In seconds.
The high-tech, lightweight chrome-moly steel frame has a knack for easy
handling, outlandish rideability, precise cornering and excellent stability.
You can also count on high torsional rigidity and low longitudinal stiffness.
This results in better absorption of the energy created from the front and
rear suspension, sucking up jumps and bumps. In short: more comfort and
less rider fatigue. Laterally attached, lightweight aluminum engine head
stays (the connection between cylinder head and frame) contribute to more
precise cornering and a reduced vibration level. The engineers were able
to pull off all that, while making their frame a big fat kilogram lighter than
that of the lightest competitor on the market. In addition, it is easier to
maintain, easier to work on and supplies more space for the tank and
other components. The bike also features an extra-light subframe made of stable
aluminum profiles, which tiptoes the scales at less than 900g.
Sophisticated ´No Dirt´ footpegs prevent smudging up the pegs, even when
digging in deep ruts. Looking for a higher riding position? Then just mount
the footpegs of the MY2017 EXC models, which are 6mm higher than the
The cast aluminum design offers low weight and a perfect flex behavior.
The single-component casting process eliminates any inconsistencies
and inherent weak points created by welding. It’s better looking too.
KTM engineers sure know how to handle handlebars. This tapered one,
made of high-strength aluminum by NEKEN, is fixed in damped rubber
mountings and has two different positions. From MY2017 onwards, the lower
handlebar clamps are separated, while on the upper side a new bridge-type
clamp guarantees more torsional stiffness. It’s also easier to replace
the bar in case it gets twisted in a nasty crash. An ODI volcanized grip sits
on the right, while on the left side of the bar a comfortable ODI lock-on grip is mounted,
which does not require any wire or glue to be fixed.
FIM noise limits are a real challenge for every manufacturer. Therefore,
KTM has put a lot of effort into the development of their exhaust systems.
All 4-strokes are fitted with header pipes that have a unique standard feature;
an additional resonator system – a small chamber connected to the pipe.
On top of that, they get a short silencer, mounted as close to the engine as
possible. You know what that means: extra mass centralization and better
rideability. An advanced internal design reduces the noise sufficiently in order to
sit safely below the FIM noise limit (112 dB(A) at 2 meter max.), while still raising
the hairs on your neck.
The KTM wheels feature lightweight, CNC machined hubs and high-end
Excel rims guaranteeing maximum stability at minimum weight. The wheels
are fitted with the latest Dunlop Geomax MX 3S tires. This set is now wider
at the rear (110/90-19 instead of 100/90-19) and the bike gets an optimized
secondary drive (14/51 instead of 13/50).
Tailored to meet the needs of the world’s fastest backsides, this durable
seat offers great comfort. For MY2017, a new cover pampers its riders
even more with better feel and grip.
A lightweight polyethylene tank with a capacity of 7.0 liters of juice.
The filler cap has an inside thread, which makes for easy
and reliable closure.
The WP monoshock has been developed with the entire frame and swingarm
architecture in mind, including the linkage system and the WP AER 48
front forks. It features machined and black anodized components and is a
valuable, high-end product compared to roughcast reservoirs. A new setting
and a softer spring perfectly match the reworked front-end set-up and its
sparkling WP color scheme lets everyone know you have excellent taste
The lightweight WP AER 48 front fork, a 48mm USD air-sprung fork developed by
WP in close collaboration with KTM, is a split fork with separate functions for
each leg. That means damping functions are on the right side, whereas the air
spring is in the left. This left leg features a two-chamber system with a capsuled
air cartridge to prevent loss of air pressure. Should the outer seal start to leak,
the internal cartridge pressure will keep the bike in position. The air spring
is easy to adjust to any rider weight via a single air valve. No special tools
are required; the air pump supplied with the bike will do just fine. The right fork
leg integrates a damping cartridge that tailors to all your damping needs.
It can be adjusted to the track conditions and the rider’s preferences with a
twist of a dial (compression from the top, rebound from the bottom, 30 clicks each).
For MY2017, the AER 48 also features redesigned outer tubes with better bending
characteristics, smoother operation and less friction. Plus: they’ve lost some
weight (265g). Right off the dealer floor, these forks are more comfortable
and more sensitive than ever. But you can still hammer the hell out of them.
Top quality, CNC machined triple clamps have been something of a KTM
trademark for years. Ensuring a precise handling, they perceptibly support
the flex characteristics, and with it the action of the forks. For MY2017,
the upper triple clamp specifically features a redesign in conjunction with
the new fork tubes. The rubber damped handlebar fixation has also been
reworked and the lower handlebar clamps are now separated, while on the
upper side a new bridge-type clamp guarantees more torsional stiffness
and can easily be replaced in case it gets twisted due to a crash. In addition,
an hour meter is fitted at the upper triple clamp in order to let the rider
know it’s time for a service. Or a cold drink.
You couldn’t brake any harder, better, faster or stronger. These high-tech
Brembo babies are combined with lightweight wave discs made by
Galfer. For MY2017, the rear brake features a 10mm longer brake pedal
and you get new, less aggressive brake pads all round.
HANDLEBAR MAP SWITCH
All 4-stroke models are equipped with a sophisticated new multi-functional
handlebar map switch, which does three things:· Activation of the traction control·
Activation of the launch control· Selection of an alternative power curve (Standard
or Advanced),The traction control is a unique feature none of the competitors can
offer so far. It guarantees more efficient traction and better control of the bike
when accelerating. You’ll especially notice this on a rainy day. Push the button
and reign supreme. With this map switch the rider can also activate the launch
control, which provides more efficient starts out of the gate so you can go for the
hole shot, time and time again. How? It simply reduces the maximum engine speed
for the very first moment of the start, in order to give you better control. Push both
buttons when the engine idles and the EFI control lamp mounted on the upper triple
clamps will let you know your bomb is live. In addition, the map switch gives the rider
the chance to select an alternative, more powerful map beside the standard configuration.
Don’t you just love the idea of a boost button?
BATTERY & WIRING HARNESS
All SX-F engines are fitted with the proven electric starter – a unique
KTM feature and a major benefit at all levels of motocross racing.
A super compact and lightweight 495g Lithium-Ion starter battery
breathes life into the engine and contributes to low vehicle weight.
The battery and wiring harness are centralized in a compartment above
the airbox, allowing the mechanic to remove the subframe without getting
in conflict with the electrics. Because a happy mechanic, is a good mechanic.
Like all KTM 4-stroke motorcycles, the 250 SX-F is started at the push of a button
- a priceless advantage when you’re on the clock.
KTM R&D, Kiska Design and all our factory riders had their say in
shaping the plastics. Their goal: complete harmony between rider
and bike. And so it turned out. Perfect ergonomics and contact points,
maximum freedom of movement, a low seat height and sweet comfort,
especially in the rear part of the seat. The I-beam structures of the front
and rear fenders are prime examples of such an intelligent design,
guaranteeing maximum stability and a low weight thanks to well
thought-out construction and mounting. Plus: they stay cleaner for longer.
A new, tailor-made kit, fit for a king. Because in this sport,
champs deserve to look the part regardless of the dirt.
|Design||1-cylinder 4-stroke engine|
|Starting aid||Electric starter|
|Clutch||Wet, CSS multi-disc clutch, Brembo hydraulics|
|Frame||25CrMo4 steel central-tube frame|
|Front suspension||WP-USD, AER 48, Ø 48 mm|
|Rear suspension||WP shock absorber with linkage|
|Suspension travel Front||310 mm|
|Suspension travel Rear||300 mm|
|Brake system||Disc brakes|
|Brake discs - diameter Front||260 mm|
|Brake discs - diameter Rear||220 mm|
|Chain||5/8 x 1/4"|
|Steering head angle||63.9°|
|Wheel base||1485±10 mm|
|Ground clearance (unloaded)||370 mm|
|Seat height (unloaded)||960 mm|
|Total fuel tank capacity approx.||7 l
Unleaded premium fuel (95 octane), mixed with 2-stroke engine oil (1:60)
|Weight without fuel approx.||98.2 kg|