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– 2006 Yamaha YZ250F 50th Anniversary Edition
YZ250F 50th Anniversary Edition
The YZ250F had, ahem, a pretty good 2005 notching awards in the 250cc 4-stroke shootouts from Dirt Bike, Motocross Action and Cycle News.
But because we’re Yamaha, we wouldn’t kick back and rest on our laurels. For 2006, there’s an all-new Twin Chamber 48mm fork, a new trick shock that calls the shots for a lighter, more rigidly mounted swingarm. You’re going to be absolutely floored by the improved feel and response, but that’s just the tip of the iceberg. We also redesigned the engine, updating the intake ports, combustion chamber, piston and ignition mapping. More control. More power. See you on the podium!
Liquid-cooled, 249cc, DOHC, 5-titanium valve, 4-stroke engine features a 13,500-rpm redline for incomparable, competition-crushing power.
Automatic decompression system means easy starting. The YZ250F restarts in any gear.
Optimized combustion chamber design provides the most efficient intake flow for maximum power.
Titanium valves and load-reduced springs decrease weight by more than 40% over a conventional valve train and reduce reciprocating mass for faster-revving, smoother-hitting power delivery across the rev range.
The cylinder features a ceramic composite coating which insures uniform heat dissipation, reduced friction and a longer service life.
Lightweight convexed shaped, forged piston matches the intake port design for fast response and great durability.
Special cylinder design features cutaways that allow the air trapped under the piston to enter a side chamber (or cutaway) to reduce horsepower-robbing “pumping losses.”
Lightweight crankcase also utilizes cutaways to reduce “pumping losses.” The crankcase cutaways match the cutaways in the cylinder.
Magnesium cylinder head cover helps reduce weight.
Revised dry sump lubrication system uses a new oil tank positioned in front of the engine. The oil is no longer held in the frame. This new oil tank is positioned lower in the chassis which centralizes mass and lowers the centre of gravity for exceptional handling and a light feeling.
New strainer chamber shape in the crankcases improves the oil circulation route and as well as reducing the oil churning resistance, which in turn reduces the ‘pumping losses”
Revised, lightweight, oil delivery hoses reduce weight.
Slick-shifting, 5-speed transmission with heavy-duty, multi-plate clutch features involute splines on the transmission axles, ensuring smoother shifting and instant hook-up under power.
Quick-access, outer clutch cover for fast, easy clutch maintenance
Revised 37mm Keihin FCR-MX37 flat-slide carburetor with throttle position sensor (TPS) ensures ultra-precise fuel/air mixing and lightning-quick throttle response. The location of the TPS has been changed, the choke knob size has been reduced and the carb settings have been optimized for maximum power.
Convenient, handlebar-mounted hot start lever ensures fast starts when the engine is hot.
New design kick start lever, ratchet and internal mechanism helps to facilitate easy starting and improve kick starter durability.
Washable, dual-stage, foam air filter provides excellent filtering qualities. The boot between the air box and the carb has been revised to provide increased rigidity.
Revised CD ignition system delivers a precise spark and monitors engine speed to ensure optimal timing for faster, stronger response at all rpms. The advance characteristics have been improved for 2006.
Ignition coil is integrated into spark plug cap to reduce weight and complexity.
Revised, compact new single core dual radiators provide outstanding cooling efficiency while the reducing weight due to optimized capacity. The rads are less tall and thinner for 2006, yet provide improved cooling Vs the 2005 rads. The directional fins inside the rad shrouds have been revised for improved air flow through the rads.
Lightweight exhaust system utilizes a 4-stage expansion format that improves the cylinder filling induced by the exhaust pulse effect, resulting in new power characteristics.
Lightweight titanium header pipe and heat shield reduces weight. Specially shaped header pipe angle maximizes engine power and allows hassle-free replacement of the oil filter.
Lightweight aluminum / stainless steel muffler reduces weight while its re-packable design maintains optimal engine performance and reduced noise levels.
Trick, works-style clutch lever features a race-spec “barrel adjuster” for on-the-fly adjustability. There is a new, larger boot covering the adjuster that provides more grip for easier operation.
All new compact aluminum semi-double-cradle frame features a cast steering head while the remainder of the frame uses forged, pipe stock and extruded components. Yamaha has maintained the semi double cradle design to allow for “controlled flex” to optimize suspension action. The new frame provides a lower centre of gravity for a light feel and razor sharp handling, plus less rider fatigue, and excellent stability. Over the years, the “knock” on aluminum frames is that they were too stiff and therefore make suspension set-up difficult and may provide a harsh ride. Yamaha has changed that with the semi-cradle design.
Removable rear sub frame is constructed of square-section, lightweight aluminum pipe. Detachable design allows easy access when servicing rear suspension components.
New, lightweight, tapered, aluminum swingarm is produced using “hydro forming”, a special forming method that uses high pressure water to form shapes. The new swingarm provides improved overall chassis balance thanks to the addition of re-enforcing ribs in the cast aluminum around the pivot area. The result is a 2% increase in torsional rigidity for improved handling.
New, cast aluminum upper triple clamp provides an increase in rigidity (longitudinal torsion) for improved handling.
New forged lower triple clamp features an increase in longitudinal rigidity which allows greater flexibility to absorb the forces applied between the front fork and the frame for improved handling.
All new Pro Taper handle bars reduce weight and improve durability.
New adjustable handlebar mounts allow the handlebars to be moved 10mm rearward if desired.
New, lighter, improved 48mm, adjustable, inverted, Kayaba cartridge forks feature a revised twin-chamber design. The twin chamber design means the damper unit is in a separate structure which prevents aerated fork oil from entering the inner damper assembly and degrading its damping abilities. Since the inner damper is pressurized, it also eliminates bubbles forming in the oil.
For 2006, the balance between the inner and outer tubes has been optimized, while the Kashima coating on the pressure tank and the piston rod reduce friction for smoother suspension performance. The cylinder diameter has been revised from 25 to 24mm for improved primary cushioning and a low friction oil seal has been used. The weight of the fork assembly has been reduced by 2.5%
The 48mm KYB fork also features a relocated Transfer Control Valve (TCV). The TCV enhances the damping force of the inner damper from mid stroke to full stroke and improves bottoming characteristics. The benefit of TCV is more precise control throughout the full stroke range. For 2006 the TCV is now located on the upside of the spring and its function is controlled by piston speed, not piston position.
“Kashima coating” has been applied to the fork tubes to reduce friction for smoother suspension performance. Front wheel travel is 300mm (11.8″).
The fork pitch (or separating width between the tubes) has been increased for 2006 for improved handling.
Front fork adjustments include: 20-way compression damping and 20-way rebound damping. Optional fork springs are available through Genuine Yamaha parts.
Large, semi-wrap-around plastic fork protectors provide excellent protection from stone / rock chips. The “self-supporting” design helps to reduce friction for smoother fork operation.
Revised Monocross link rear suspension system features a fully adjustable, Kayaba, piggyback shock which provides 315mm (12.4″) of wheel travel and features separate adjusters for high- and low-speed compression damping. Adjustments include: spring preload, 20-way rebound damping, 20-way low-speed compression damping and 2 turns of high speed compression damping.
The damper rod diameter in the 2006 KYB shock has been increased from 16 to 18mm while sub tank capacity has been increased by 30% for improved shock performance, Kashima coating is used in the shock body and sub tank to reduce friction and improve suspension performance during a long moto.
All new, trick titanium shock spring reduces weight by 500 grams. This is a significant weight reduction since it is unsprung weight that has been reduced. A reduction in “unsprung” weight , causes a dramatic effect on suspension performance. The new titanium spring provides outstanding strength, and durability, combined with reduced weight.
The 2006 Kayaba shock utilizes a full rebound oil lock system for excellent suspension function and great ride quality.
250mm floating front disc brake utilizes lightweight, aluminum pistons in its twin piston caliper for excellent stopping power and feel. Shortly style adjustable front brake lever.
245mm rear disc brake with single piston caliper uses an integrated master cylinder (fluid reservoir is integrated into the top of the master cylinder) for strong stopping power with excellent feel and control.
New rear brake caliper not only improves rear braking efficiency but also sits lower on the swingarm to reduce the center of gravity. The new caliper features a new, plastic caliper protector and a 30% lighter lower disc protector.
All new “slim line” body components include: front and rear fenders, rad shrouds, side covers /number plates, and seat. The seat foam has been revised for more cushioning effect and improved rider comfort. The new body design gives the all new 2006 YZ450F a new lighter more modern look plus allowing for fast, easy rider movements.
Specially designed “Sun Star” rear sprocket increases the contact area between the sprocket and chain rollers, thereby reducing the load on the chain and increasing the service life of both chain and sprocket.
Lightweight, 21″ front and 19″ rear Excel rims provide exceptional durability and help reduce unsprung weight for optimal suspension performance and handling.
New rear wheel collar is tapered to allow for faster, easier wheel removal installation.
Lightweight, 21″ front and 19″ rear Excel rims are exceptionally durable and reduce unsprung weight.
Dunlop knobby tires offer competition-spec traction and excellent wear.
New “flat-design” seat features multi density foam that provides good initial softness / comfort and then increases the firmness as more pressure is applied. The seat is raised 10mm for 2006. The “pebble” or “gripper” finish on the top and side surfaces provides excellent rider grip and durability.
New stainless steel coated exterior nuts and bolts for improved appearance.
Large fuel cap and filler hole ensures easy opening and fast, hassle-free refueling.
Lightweight, titanium footpegs provide excellent grip and ground clearance.
Cleated, rear brake lever and folding shift lever tip offer superb grip and exceptional durability.
Stainless steel, inner clutch cable provides excellent strength and long life.
Re-packable exhaust silencer means a rider can maintain optimum engine performance and reduced noise levels.
Rugged aluminum main engine skid plate
Engine 4-stroke, liquid-cooled, DOHC, 5-valvew/titanium valves, single
Bore and Stroke 77 x 53.6mm
Compression Ratio 12.5:1
Maximum Torque 2.9kg-m (21 ft-lb) @ 8,500 rpm
Fuel Delivery Keihin FCR37, flat-slide w/throttle position sensor
Ignition Digital CDI
Transmission Constant mesh, 5-speed
Final Drive Chain
Suspension (Front) Fully adjustable 48mm inverted fork
Suspension (Rear) Fully adjustable link Monocross
Brakes (Front) 250mm floating disc
Brakes (Rear) 245mm disc
Tires (Front) 80/100-21
Tires (Rear) 100/90-19
Length 2,176mm (85.7”)
Width 815mm (32.1”)
Height 1,292mm (50.9”)
Wheelbase 1,485mm (58.5”)
Seat Height 983mm (38.7”)
Dry Weight 93.5kg (205.7lb)
Fuel Capacity 7 litres (1.6 imp. gallons)