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KTM 250 SX-F 2018:SMALL-BORE SUPERSTAR

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The KTM 250 SX-F has been on top of the MX2 World Championship for many years now and just added another world title to its crowded trophy cabinet. But that’s no surprise. The combination of a powerful and torquey engine in a lightweight and agile chassis is bound to place the KTM 250 SX-F onto podium after podium.

 

ENGINE

The KTM 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 E-starter.

 

 


 

CYLINDER HEAD

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

cam followers with a hard DLC coating.

 

 

 

CRANKSHAFT

The KTM 250 SX-F’s crankshaft utilizes a short connecting

rod, which makes for an overall compact and lightweight

engine with a snappy power delivery. A plain big

(bottom) end bearing with two force-fitted bearing

shells runs directly on the crank pin. The necessary oil

feed for this bearing is ensured by the engine’s pressurized

lubrication. This design is a decisive benefit in terms of the

crankshaft service interval, which can be lengthened

due to the plain bearing. So just pin it, all day long.

 

 

 

 

E-STARTER

The KTM 250 SX-F is fitted with a unique E-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 will fire time and time again at the push of

a button. Even under extreme conditions, thanks

to its more heat resistant O-ring.

 

 

 

CRANKSHAFT

This reliable piece of engineering has been skillfully balanced

to guarantee minimal vibrations. In its latest form, it

allows a decrease of the displacement to 125cc just by

replacing cylinder, piston and head. There’s no more

need to change the crankshaft. Two-in-one in no time.

 

CRANKCASES AND ENGINE COVERS

The design of the die-cast crankcases allows for minimal

weight and 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, which reduces

the wear caused by the rider’s boots. This way,

your SX-F will keep looking better longer.

 

TRANSMISSION

The reliable 5-speed transmission features a special

surface treatment on the 2nd, 3rd and 4th gears

for solid reliability. The advanced ´No Dirt´ gear shift lever

design prevents dirt from jamming the joint of the lever and

guarantees precise shifting even in the muddiest conditions.

All 4-stroke SX-F engines are fitted with a gear position sensor

for tailored engine mapping for each gear. In MY18, the

transmission shaft gets a new C4 bearing that has a bigger

overlap in the case. This means reliability even under

extremely hard conditions. Think GP-level riding.

In knee-deep sand.

 

 

 

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.

 

 

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.

 

 

CLUTCH

The KTM 250 SX-F employs the KTM-developed CSS

clutch (coil spring steel) with a robust steel basket and

extremely heat resistant clutch plates and new, nitrated steel

liners reducing the wear. Light operation and telepathic amounts

of control are standard with this hydraulic Brembo

actuated clutch.

 

 

 

BALANCER SHAFT

The side-mounted balancer shaft does double duty also

driving the water pump. Thanks to its perfect balance and

low oscillating masses, engine vibration is kept to a minimum.

 

COOLING SYSTEM

KTM’s proven cooling system routes the coolant from

the cylinder head through the frame triangle, directly

to aluminum radiators made by WP. Thanks to flow optimized

internal circulation and CFD-calculated ventilation, the system is

superbly efficient. In addition, new radiator protections improve

heat dissipation. Especially in the mud. They are also integrated

into the front part of the shrouds to protect the

radiators in a crash.

 

Weight

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.

 

FOOTPEGS

Sophisticated ´No Dirt´ footpegs prevent clogging of the

footpeg pivot, even when digging in deep ruts. Looking

for a higher riding position? Then just mount the footpegs

of the MY2018 EXC models, which are 6mm higher

than the SX versions

 

EXHAUST

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 headers

that have a unique standard feature; an additional resonator

system – a small chamber connected to the pipe. All 4-strokes

are fitted with a short silencer, mounted as close to the

engine as possible. You know what that means: extra mass

centralization and better rideability. Its advanced internal design

reduces the noise sufficiently in order to sit safely

below the noise limit, while still raising the hairs on your neck.

 

FRAME

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.

 

 

 

AIR FILTER BOX

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.

 

SWINGARM

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.

 

 

 

HANDLEBAR

KTM engineers sure know how to handle handlebars. This

tapered one, made of high-strength aluminum, is fixed

in damped rubber mounts and has two different positions.

ODI lock-on grips make grip changes easy and

do not require any wire or glue to be secured.

 

 

 

FUEL TANK

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.  

 

 

.

 

WHEELS

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.

 

 

Shock absorber

The WP shock absorber has been developed with the entire

frame and swingarm architecture in mind, including the

linkage and the WP AER 48 front fork. It features machined

and black anodized components and is a valuable, high-end

product compared to roughcast reservoirs. A new,

confidence inspiring setting with improved damping characteristics

perfectly matches the front-end setup and its sparkling

WP color scheme lets everyone know you have

excellent taste in suspension.

 

 

FORK

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 2-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). Right off the dealer floor, this fork (with reworked

damping characteristics) is more comfortable and more

sensitive than ever. But you can still hammer the hell out of it.

 

TRIPLE CLAMP

Top quality, CNC machined triple clamps have been a KTM

trademark for years to ensure precise handling. The rubber

damped handlebar fixation allows for two positions and

an hourmeter is fitted in order to let the rider know it’s

time for a service.

 

 

BRAKES

These high-tech Brembo babies are combined with

lightweight Wave brake discs. You couldn’t brake

any harder, better, faster or stronger.

HANDLEBAR MAP SELECT SWITCH

All 4-stroke models are equipped with a multi-functional

handlebar map select 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 that none of the competitors can offer. It

guarantees more efficient traction when the track conditions

are less than perfect. Push the tip switch and reign supreme.

With this map select switch the rider can also activate the

launch control, which provides more efficient starts out of the

gate so you can go for the holeshot, 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 tip switches when the engine idles and the

EFI control lamp mounted on the upper triple clamp will let you

know you are READY TO RACE. In addition, the map select

switch gives the rider the chance to select an alternative,

more powerful map beside the standard configuration.

Welcome to the future.

BATTERY & WIRING HARNESS

A strong new lithium ion battery breathes life into the engine

and contributes to low vehicle weight. The lightweight

battery and wiring harness are centralized in a compartment

above the air filter box, allowing the mechanic to

remove the subframe without getting in conflict

with the electronics. A happy mechanic is a good mechanic.

E-STARTER

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.

 

BODYWORK

KTM R&D, KISKA Design and all our factory riders had their

say in shaping the plastics with one goal: complete harmony

between rider and bike. Perfect ergonomics and contact points

provide maximum comfort in movement on the SX-F. The I-beam

structures of the front and rear fenders guarantee maximum

stability and a low weight thanks to well thought-out

construction and mounting. They also stay cleaner for longer.

 

GRAPHICS

A new, tailor-made kit and a Factory orange frame. Because

in this sport, champs deserve to look the part regardless of the dirt.

 

 

 


    

 

 

TECHNICAL DETAILS

 

ENGINE

 

Design 1-cylinder, 4-stroke engine
Displacement 249.9 cm³
Bore 78 mm
Stroke 52.3 mm
Starting Electric starter
Transmission 5-speed
Primary drive 24:73

Secondary gear ratio

14:51
Clutch Wet, CSS multi-disc clutch, Brembo hydraulics
EMS Keihin EMS
   
   

 

Chassis

 

Frame design

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

Front brake

Disc brake

Rear brake

Disc brake

Front brake disc diameter

260 mm

Rear brake disc diameter

220 mm

Chain

5/8 x 1/4"

 

Steering head angle

63.9 °

Wheelbase

1485 ± 10 mm

Ground clearance

370 mm

Seat height

960 mm

Tank capacity (approx.)

 7 l

Weight READY TO RACE (without fuel)

98.2 kg

 

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