Yamaha WR 250F

Tight woods or wide open terrain, the lightweight, compact 2008 Yamaha WR250F is ready to tackle any challenge you can throw at it. The combination of a smooth, powerful engine, a lightweight aluminum chassis with YZ based syspension and great brakes make the Yamaha WR250F an amazing off road performer.

Discover the beauty of balance -- For riders who favor finesse over brute force, the 2008 WR250F is the way to go off-road.

Based on the latest version of our YZ four stroke motocrossers, the WR250F features a lightweight aluminum frame and swingarm, stylish "slim line" bodywork specially designed to provide excellent rider maneuverability and YZ based suspension and brakes fore and aft.

We've even engineered the seat for enduro use, knowing that a rider will be in the saddle all day. Strong, dependable performance, all day rider comfort … just two of the keys to the WR's success.

FEATURES:

Liquid-cooled, 249cc, 5-valve, DOHC, 4-stroke powerplant with super light titanium valves is based on the current YZ250F engine design. The WR250F engine features different camshafts, ECU and exhaust system than the YZ250F for improved low to mid range power which is better suited to enduro type riding.

Super convenient electric starting means fast, sure starts. The electric starter is also backed up by a manual kick starter.

Hassle free automatic decompression system ensures fast restarts in any gear.

Convenient, handlebar-mounted hot start lever for easy restarts when the engine is hot.

Magnesium cylinder head cover helps reduce weight.

Optimized combustion chamber design provides the most efficient intake and exhaust flow for maximum engine performance

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.

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."

The crankcase also utilizes cutaways to reduce "pumping losses." The crankcase cutaways match the cutaways in the cylinder.

Dry sump oil tank is located in front of the engine between the frame tubes for protection. This design centralizes mass and reduces the centre of gravity for improved handing and a lighter feel.

The crankcase features a "tri-axis" design for the crankshaft, main and drives axles. This tri-axis design keeps the crankcases more compact while also centralizing mass for better handling. All of the shafts are positioned low in the cases to maintain a low centre of gravity for great handling and maneuverability.

Special "enduro focused" camshafts (intake & exhaust) provide outstanding low to mid range power well suited for off road use. The cam timing and event angle are different than the YZ250F.

Balancer shaft reduces vibration for improved rider comfort and reduced rider fatigue.

Lightweight crankshaft provides fast throttle response.

Lightweight, short-skirt, forged piston provides great durability and its lightweight design means faster engine response.

Oil volume in engine has been optimized to reduce weight and oil "drag" related power losses.

Compact design automatic cam chain tensioner reduces maintenance and mechanical engine noise.

37mm, Keihin FCR, flat-slide carburetor with TPS (throttle position sensor) provides excellent throttle response.

ECU features 3D ignition mapping to accommodate the engine power characteristics. The ECU provides optimal timing at all rpms for fast engine response.

Lightweight direct ignition coil is integrated into the plug cap to reduce weight and complexity

Wide ratio 5-speed transmission features gear ratios designed for enduro type riding and that match the engine power characteristics.

Heavy-duty clutch matches engine output and offers a light, progressive clutch feel with less lever effort for smoother shifting.

Quick-access, lightweight aluminum outer clutch cover allows fast, easy access to the clutch.

New stylish mat black finish on left & right side crankcase covers, oil filter cover and sprocket cover for improved appearance.

YZ based compact dual radiators provide optimum cooling and feature a re-enforcing bar to help protect the rads in the event of a tip over.

Washable, dual-stage, foam air filter can be accessed without tools via "Dzus-type" fasteners. The air box is secured to the frame via only one bolt for fast removal.

Lightweight exhaust system features a stainless steel header pipe with titanium heat shield, aluminum muffler and titanium rear cone. This system maximizes engine power and allows hassle-free replacement of the oil filter.

Lightweight aluminum wrapped muffler offers an 82 dba noise level (stock settings). This muffler features a "serviceable", screen-type spark arrestor which prevents sparks from exiting the exhaust.

Oversize race type "barrel adjuster" for easy, on-the-fly adjustability of clutch lever/cable play.

AIS (air induction system), located on front side of cylinder head reduces harmful emissions.

Lightweight, 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. This frame design provides a low centre of gravity for a light feel and razor sharp handling, plus less rider fatigue, and excellent stability.

Removable, aluminum rear sub frame constructed of square-section pipe reduces weight and provides easy rear suspension access.

Lightweight, tapered, aluminum swingarm is produced using "hydro forming"; a special forming method that uses high pressure water to form shapes.

48mm, adjustable inverted, Kayaba cartridge fork provide excellent suspension performance. Front wheel travel is 300mm (11.8").

Front fork adjustments include: 20-way compression damping and 20-way rebound damping. Optional fork springs are available through Genuine Yamaha parts.

Large plastic fork protectors wrap around the fork tubes for increased protection against dirt, mud and stone chips. These fork protectors are self-supporting to reduce friction for smoother fork operation.

Forged aluminum upper and lower triples clamp reduce weight and provide increased strength.

Adjustable forged handlebar mounts allow the handlebars to be moved 10mm rearward if desired.

High tech, lightweight, Pro-Taper aluminum handlebar with reinforcing crossbar and foam pad.

Monocross rear suspension system features a fully adjustable, Kayaba piggy back style shock with separate adjusters for high- and low-speed compression damping.

Shock adjustments include: spring preload, 20 clicks of low-speed compression damping, 2 turns of high-speed compression damping and 20 clicks of rebound damping. Rear wheel travel is 310mm (12.2").

Link-type rear suspension provides a rising rate (progressive) suspension function. The linkage design is virtually the same as YZ-f series of MX bikes.

250mm fully floating front disc brake with "wave style" rotor is squeezed by a twin piston Nissin caliper fitted with lightweight, aluminum pistons provides excellent braking performance. The pins that the disc floats on have been shortened to reduce weight.

"Shorty style" adjustable front brake lever.

245mm rear disc utilizes a lightweight "wave style" rotor. The Nissin single piston caliper and an integrated rear master cylinder (fluid reservoir is integrated into the top of the master cylinder to reduce weight) delivers strong, progressive stopping power with excellent control and feel.

New design rear brake lever provides excellent feel

Rugged, Excel 21" front and 18" rear rims provide exceptional durability and help reduce unsprung weight for optimal suspension performance.

High tech, lightweight digital meter assembly. This compact meter features: speedometer, dual tripmeters, odometer and a clock in the basic mode. Or in the "race mode", pace management functions such as timer, and distance compensating tripmeter.

Rugged "slim-line" bodywork is very similar to the YZ-F counterparts. This "slim line" bodywork allows fast, easy rider movements and a lighter overall machine feel.

Seat is based on YZ-F style but is wider with more padding for improved rider comfort during a long ride.

Stylish slim design front headlight is compact and offers 35 watts of lighting power. The headlight beam is adjustable up and down.

Slim design compact LED taillight is tucked out of the way to prevent damage

Revised 8 liter black plastic fuel tank is designed to allow easy rider movements. This revised tank features a special "fluorination surface treatment" which reduces fuel permeation for improved environmental protection. The fuel line and tank vent hose are made of "fluororubber" to also reduce the escape of fuel vapors into the atmosphere.

Lightweight aluminum kickstand is designed to allow lots of Ground Clearance.

Heavy duty one piece resin plastic engine guard. Only 3 bolts hold it in place for easy removal when washing the bike.

Extra wide 55mm stainless steel foot pegs provide excellent grip.

Premium Dunlop knobby tires

8-litre fuel tank with convenient on/off/reserve petcock for peace of mind

Serrated rear brake lever and folding shift lever tip

Rugged, plastic, lower rear disc and rear caliper protectors

New, sealed, low-maintenance 6 amp hour battery is gel-filled type to prevent leaks in the event of a tip-over.

Waterproof starter button and engine kill switch are handlebar-mounted.

Lightweight chain guide / support helps reduce chance of chain derailment. Also helps protect rear sprocket damage too.

Heavy duty rubber swingarm protector

Heavy duty "O" ring chain for durability

Review

The huge changes to Yamaha's '05 YZs might lead you to believe the motocross effort soaked up all the R&D, but it looks like there was plenty left for the off-road bikes as well. Yamaha's newly released WRs feature a slew of changes, both major and minor, aimed at creating lighter, more agile and more user-friendly machines. We got our grubby paws on the newly released WR 250 and 450 at California's Hungry Valley and immediately headed out for some bushwhacking.

The biggest changes Yamaha emphasized were a lowered center of gravity and lowered seat height for both the 250 and 450. WRs have a history of being tall and top-heavy, but the '05s are a marked improvementit looks like the chronic problem has been solved. The WRs now carry their (lighter) weight much lower. Yamaha raised the steering head tube, but the fork is the same length, so the engine and more importantly the crankshaft are carried lower. Plus the shock is 3mm shorter, which balances out the bike and makes it lower overall compared to 2004. Overall, the seat height was decreased by 10mm on the 250, and 20mm on the 450. YZ shrouds and radiators complete the package by slimming down both bikes. Both models were much more willing to change directions in tight conditions. It was much easier to get leaned over in corners and maneuver through thick, tight brush.


2005 Yamaha WR450 features... read full caption
2005 Yamaha WR450 features more refined power, giving it easier roll-on.We didn't actually test the bikes in showroom stock condition. We replaced the WR throttle stopsthat limit the throttle opening to about halfwaywith YZ units that allow full throttle travel. We also removed the new-for-2005 tiny end baffle and unplugged the grey wire under the tank, since that was the way we rode our 2004 bikes, and it was the most equal comparison. The WR250F received an increase in power while the focus on the 450 was to refine its big power for easier roll-on. The 250 has more bark and decent bottom-end grunt, but best showcases its new power on the top endit screams. The 450's bark was partially calmed by reducing the compression ratio. It still has big power, but now comes in a more manageable package. The lower center of gravity coupled with the smoother low-to-mid delivery made huge improvements in the 450s agility.

The WRs received new 48mm forks, although not the same KYB fork as the other '05 blue bikes. The beefy new front suspension is much more rigid than the plush feel of the '04s. With the stock settings, the front end was too stiffpushing in sand washes and dancing around on rocks or bumpy hard-pack. We softened up the compression between two and six clicks depending on the size and speed of the rider. We also went out two clicks on the fork rebound. The action of the fork and the steering precision of the bike is very closely tied to the sag. You'll want to be careful to set it between 100 and 105 millimeters. The shock soaked up chop fairly well, and pounded through whoops better than ever.


The WR450 is now green sticker... read full caption
The WR450 is now green sticker legal; anticipate the same for the 250 in '06.Yamaha also addressed EPA an CARB regulations in their re-design. The new USFS-approved aluminum exhaust with spark arrestor is Federal noise level legal at 82dba. With the baffle out, it still registers under 96dba, meeting California regulations. The 450's newly designed air induction system also makes it green-sticker ready (a much-welcomed change for Californians tired of being shut down the instant rangers catch a glimpse of blue plastic). Expect the 250 to be green sticker-able in '06.

Source Dirt Rider