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TECHNOLOGY


ENGINE

A hot start system gives quick starts when the engine is hot. The hot start lever is unitised with the clutch lever.

NEW - Increased spring set load for the auto-decompressor located on the exhaust cam shaft contributes to easier starting

Additional performance-oriented engine characteristics

The engine was tuned such that the torque curve follows the limit of running resistance for as long as possible.(Unchecked, engine torque can exceed this limit, resulting in wheel spin, which does nothing to help forward momentum.)

Efforts were made to achieve the widest possible torque band, so that traction efficiency would be maximized for a greater part of the rev range.

Lightweight titanium valves (IN: 31mm; EX: 25 mm) reduce reciprocating weight and offer high-rpm reliability. The ultra-light valves have extremely thin valve stems on par with those found in supersport machines. The intake valves feature thicker heads for increased strength and both intake and exhaust valves are formed from a new, highly rigid, titanium material.

Crank web design increases offsetting moment for a high crankshaft balance factor. At close to 60%, the balance factor of the ’10 KX250F is on par with our factory racers. The result is reduced engine vibration, smoother power delivery and increased performance in the mid-high rpm range.

Sprocket-style chain drive roller helps smooth engine braking by reducing the effect of driveline lash when the rider gets off the gas quickly and play in the lower side of the chain suddenly tightens. The additional control facilitates corner entry.


CHASIS

NEW - Large synthetic skid plate offers great protection with minimum weight.

NEW - Revised front fender is thicker and more rigid.

NEW - New chain with thinner inner links offers offers 20g in weight savings.           


Factory-style chassis components and tuning

The KX250F’s slim aluminum perimeter frame is a lightweight construction composed of forged, extruded and cast parts. Chassis balance and settings were all set to suit race-experienced riders. The centre of gravity and key dimensions (swingarm pivot, output sprocket and rear axle locations) were chosen so that the rear tire would drive the bike forward (instead of causing it to squat). For ’10 revisions to the swingarm and suspension components were designed to offer greater cornering performance, optimized front-rear balance and greater stability on corner entry thanks to reduced “kicking” (tendency of an overworked rear shock to cause the seat to rise, hitting the rider in the rear).

Quicker-turning chassis

NEW - New steering stem shaft with lower rigidity contributes to lighter handling.

NEW - Swingarm with revised cross-section, wall thickness and internal ribs contributes to improved cornering performance, enabling lighter turn-in and tighter cornering.

The alloy swingarm uses a cast front section, tapered hydroformed spars and forged chain adjusters.       


SUSPENSION

Race-oriented suspension

Showa twin-chamber fork keeps oil and air in separate chambers for stable damping performance during long motos.

NEW - Revised settings for ’10 optimize the front/rear balance, resulting in a flatter (less forward-leaning) chassis posture when riding. Further, revised damping settings and a less rigid steering stem offer improved action(smoother) and increased absorption performance.

A super-hard titanium coating on the outer surface of the inner fork tubes reduces sliding friction (and stiction) and improves action, contributing to the smoother ride. The increased surface hardness of the dark navy blue coating also helps to prevent scratches and damage to the tubes.

Friction-reducing Kashima Coat on the inside of the fork outer tubes contributes to smoother suspension action (especially at the initial part of the stroke) and a better ride feel.

NEW - Revised shock damping settings offer increased absorption performance, reducing the chance of “kicking” for easier corner entry.

The rear shock features dual compression adjustability, allowing high-speed and low-speed damping to be tuned separately.

The rear shock also features the Kashima Coat on the tank cylinder. The reduced friction smoothes suspension action.


PERFORMANCE-RELATED MODIFICATIONS

NEW - New piston (like that of the 2010 KX450F) features the same design used on our factory racers. A revised profile with a shorter skirt, reinforced external ribs and the first mass-production use of a bridged-box bottom, featuring fully flush internal bracing, results in a lighter, stronger piston.

NEW - Shorter piston pin contributes to reduced reciprocating weight.

NEW - A revised piston crown contributes to improved combustion.Cylinder height increased accordingly to maintain compression ratio at 13.2:1.

NEW - Exhaust pipe dimensions revised (non-tapered part is longer), for increased low-rpm performance.


FACTORY-STYLE AND OTHER RACE-ORIENTED COMPONENTS

Among the KX250F’s numerous factory-style components are its front and rear petal disc brakes. In addition to helping reduce unsprung weight, the wave shapes of the petal discs help clean the brake pads for more efficient braking performance.

New Revised rear brake pad material offers stronger braking performance.

Rear caliper guard protects the caliper from damage.

A factory-style Renthal (standard-type) aluminum handlebar is standard equipment.

Rib-less rear hub and butted spokes reduced unsprung weight.

New rim design with revised cross section offers both increased strength and lighter weight.(F: -20 g; R: -60 g)

Rims are coated in black alumite – just like our factory racers.

Factory-style graphics complement the KX250F’s highly tuned performance.


MODIFICATIONS FOR ENHANCED DURABILITY AND RELIABILITY

NEW - Electrofusion treatment on cylinder bore results in a surface with good oil retention. Further, the molybdenum on the surface of the cylinder bore helps resist scorching, contributing to durability.

NEW - Wider (18mm >> 19 mm) big-end bearing featuring thicker copper plating on its cage, and a longer crank pin offer increased reliability.

NEW - Revised oil pump rotors offer increased reliability and durability. Feed pump rotor size is larger (5 mm >> 5.5 mm), increasing oil flow; scavenge pump rotor is smaller (11 mm >> 10.5 mm), reducing mechanical loss.

NEW - Larger dogs on the 3rd and 4th input gears help prevent wear, and revising the 4th input gear holding method (by eliminating a circlip and washer and changing the shape of the 2nd input gear) reduces thrust clearance. These changes offer increased shifting reliability.

NEW - Crankcases with revised engine mounts and increased thickness are stronger, contributing to enhanced durability.

NEW - New thicker (22 mm >> 32 mm), wider (113.8 mm >> 117.8mm)radiators with increased fin and tube pitch are stronger, offer better resistance to mud build-up, and maintain cooling performance. Because the new radiators are stronger, reinforcing brackets could be eliminated, resulting in lower overall weight. (These radiators feature the same construction as those on the 10MY KX450F.)

NEW - Exhaust pipe’s new stainless steel construction is more durable. Revised joint between the exhaust pipe and muffler offers increased sealing performance. Rubber damper collar used for the rear silencer mount also contributes to increased durability.


RIDER INTERFACE

Wide (front-to-rear) footpegs designed to offer grip and superb feel at the pegs.
Designed with rider ergonomics in mind, bodywork components offer the rider a slim interface, the natural position making it even easier for racers to go fast.

NEW - Formed using a double-injection moulding process, the 2-tone shrouds contribute to the slim package. Fine-tuned to accommodate the new radiators, the shrouds feature a slightly slimmer design.

2-tone side covers are also formed using a double-injection moulding process. Like the shrouds they contribute to the slim package. A hole in the right-side cover helps cool the silencer.

The frame widens at the ankles to offer the rider better grip and narrows near the bend below the seat to allow a slim riding position.

NEW - Slim seat features firmer urethane which keeps its original shape longer.

The seat uses a slip-resistant top surface for good grip when seated and smooth sides for excellent rider mobility.

Wide (front-to-rear) footpegs designed to offer grip and superb feel at the pegs.

The clutch cable boot features a large quick adjuster, making it easier for riders to adjust play in the clutch cable.

Throttle grip has a unitised collar. The one-piece unit provides additional stability during throttle operation.

Lightweight short-length grips feature a pattern designed to provide excellent grip.


OPTIONAL FEATURES

Optional engine parts include magneto rotors with different inertias (3.6, 4.8 kg cm2; STD: 4.4 kg cm2) and a 12T output sprocket (STD: 13T).

Optional chassis parts include handlebar holder for a ø28.6 mm bar (STD: ø22.2mm), aluminum and steel rear sprockets (46-50T; STD: 48T), solid petal brake rotors for wet races, different springs for the front fork and rear shock, and manual decompression lever & cable.

SPECIFICATIONS


ENGINE

Type     Liquid-cooled, 4-stroke Single
Displacement     249 cc
Bore and Stroke     77.0 x 53.6 mm
Compression Ratio     13.2:1
Fuel System     Carburetor: Keihin FCR-MX37
Valve System     DOHC, 4 valves
Ignition     Digital AC-CDI
Starting     Primary kick
Lubrication     Forced lubrication, semi-dry sump

DRIVETRAIN

Transmission     5-speed, return
Final Drive     Chain
Primary Reduction Ratio     3.350 (67/20)
Gear Ratios: 1st     2.142 (30/14)
2nd     1.769 (23/13)
3rd     1.444 (26/18)
4th     1.200 (24/20)
5th     1.045 (23/22)
Final Reduction Ratio     3.692 (48/13)
Clutch     Wet multi-disc, manual

FRAME

Type     Perimeter, aluminum
Wheel Travel: Front     315 mm
Wheel Travel: Rear     310 mm
Tire: Front     80/100-21 51M
Tire: Rear     100/90-19 57M
Caster (Rake)     27.4°
Trail     118.6 mm
Steering Angle (left/right)     42° / 42°

SUSPENSION

Front: Type     47 mm inverted twin-chamber telescopic fork
Compression Damping     16-way
Rebound Damping     16-way
Rear: Type     New Uni-Trak
Compression Damping     13-way (low-speed), 2-turns or more (high-speed)
Rebound Damping     17-way
Spring Preload     Fully adjustable

BRAKES

Front: Type     Single semi-floating 250 mm petal disc
Caliper     Dual-piston
Rear: Type     Single 240 mm petal disc
Caliper     Single-piston

DIMENSIONS

Overall Length     2,170 mm
Overall Width     820 mm
Overall Height     1,270 mm
Wheelbase     1,470 mm
Ground Clearance     340 mm
Seat Height     955 mm
Curb Mass     105.0 kg (231.5 lbs)
Fuel Capacity     8 litres

DETAILS

MSRP         $8,499

Colour         Lime Green with factory-style graphics