2003 Yamaha WR250F WR450F

Kevin Duke | March 12, 2003
2003 Yamaha WR250F - 450F

WR Stands For Wild Ride!

Yamaha has carved its own little niche in the enduro market with the successful WR series. Part of the reason why is that the blue bikes are heavily based upon their YZ motocross brothers. Rather than mild trail bikes like most of its competitors, the WRs are just a small step away from being competition-ready.

As an indication on how important this market is to Yamaha, the WR series now has its own engineering group separate from the YZ team at YMC. This and more was explained to us at the bikes’ introduction at the fantastic Hungry Valley State Vehicle Recreation Area near Gorman, CA.

The new WR team didn’t have to work long hours on the 2003 WR250F and WR450F, as nearly all the changes to the new 4-stroke YZs apply to the WRs. The chief differences are the addition of a headlight, taillight, voltage regulator, tripmeter, 18-inch rear wheel, a larger, 2.6-gallon fuel tank, a wide-ratio (WR, doncha know) transmission and a U.S. Forest Service-approved spark arrestor.

The family resemblance continues, as both WRs share much DNA. Suspension, wheels, frame, chassis geometry, bodywork, seat and brakes are virtually identical between the 250 and 450.

2003 Yamaha WR250F - 450F

But the big WR news for ’03 is the arrival of electric starting. Four-strokes have a notorious reputation for being finicky starters, but the compact new starter system makes that peccadillo obsolete. And if for some reason you end up with a dead battery, the new auto-decompression mechanism makes kicking over either bike almost as easy as a 2-stroke. For easier restarts when the engine is hot, both bikes are now equipped with a handlebar-mounted hot-start button rather than down on the carburetor as previous. 

Many more similarities are evident. Also shared is the new bodywork that features a fuel tank that is lower and much flatter (and slightly smaller). This combined with a new seat that extends almost all the way over the tank allows a rider to position his weight over the front end in gnarly corners. A new airbox has trick quarter-turn Dzus fasteners that make checking the condition of the air filter a quick process that requires no tools.

The chassis geometry of the pair is within a hair of each other, with the 450 having a scant 5mm longer wheelbase. Technology advances in metallurgy have come up with a new, super-high-tensile steel that is used on the new frames. Yamaha says it is 25% stronger than chrome-moly steel and thus the frame can be made more than three pounds lighter. A detachable, square-tube aluminum subframe is lighter than the round-tube unit it replaces.

The 46mm inverted fork is almost a full pound lighter and it carries revised damping. At the rear, an all-new, more rigid tapered swingarm (with a new anodized treatment) is worked by a revised shock that has separate high- and low-speed compression damping adjustments. Brakes have received several upgrades for ’03. Both front and rear master cylinders are lighter (the rear with a new fluid reservoir integrated with the master cylinder), and they actuate a 250mm disc up front and a 245mm rotor in the rear.

2003 Yamaha WR250F - 450F
Yamaha extended the seat over the new, flatter tank for 2003, giving a rider more body positioning options.

Even the engines, which are completely different, share similar upgrades. Crankcase pumping losses are reduced by holes connecting the cylinder and case, resulting in one free extra pony in the 450’s crowded corral; no stats were available for the 250.

For less weight and a lower center of gravity, Yamaha has slightly reduced the oil capacity and has lowered the reservoir in the frames, and a new paper oil filter is claimed to do a better job than the brass unit used previously. New “stick” coils incorporate the ignition coils with the spark plug wire for less weight and a hotter spark. A titanium exhaust pipe and heat shield reduces weight a claimed 30%, rounding out a host of changes common to both bikes.

Yamaha has gone to great lengths to find places to slice weight, and nowhere is that more evident than in the 450’s new engine. Despite the additional 23cc from the old WR426, most engine components have lost weight – everything got miniaturized. From the top, a new cylinder head loses almost half a pound, and shorter valve stems make for 12% lighter titanium valves.

Reciprocating engine parts with less mass result in a quicker revving motor, and Yamaha has pointed the 450 in that direction. A new crankshaft has lighter counterweights, saving 570 grams (1.25 pounds) and reducing inertial mass by a significant 20%. Pistons are lighter (7%), as is the new, smaller oil pump (20%).

2003 Yamaha WR250F - 450F
Mmm… trick titanium pipe save weight.

A 39mm Keihin carb is the same size as on its YZ brother, but it is a different mixer that is equipped with an anti-backfire valve. The 450 retains the 5-speed transmission from the 426 unlike the new YZ that has the fifth cog lopped off in ’03. Using the WR250’s top triple clamp has moved the handlebars 10mm further forward.

All that trimming of fat can’t quite compensate for the addition of the new starting system, including the 4.5-pound battery, starter motor and 500-watt alternator. The new 450 has gained eight pounds, according to Yamaha’s specs, to a dry weight of 248 pounds. Measured on our Intercomp digital scales, our test bike weighed in at 262 pounds with the tank empty.

It won’t take much more than 10 seconds to come to the conclusion that the extra octet of pounds means nothing. Thumb the starter and the big Thumper fires up without giving your leg a workout. Then get ready to light the fuse: This thing has mondo power, with boosts from the bottom to the top.

They don’t quite work that way out of the crate, though. EPA-mandated noise restrictions for off-road bikes neuter the stock bikes. “It’s bad,” said one of the Yamaha men about the restricted WRs at the introduction. “They’re slow.”

Thankfully, we didn’t bother to find out how bad they are in their emasculated forms, as our test bikes were in the de-restricted form. Just three components need to be removed: the stock muffler baffle, the airbox restrictors, and the throttle stop. 

2003 Yamaha WR250F - 450F
Removing these three parts from the WR (air restrictor, muffler baffle and throttle stop) dramatically increases power over stock.

Suitably modified, the 450 is a ripper for an enduro bike. The one key difference from the hugely powerful YZ450F motocrosser is a milder intake camshaft to give more grunt off the bottom. It works, as there’s good squirt available everywhere along the powerband. A rider has a choice of gears in any given situation, with lots of low-end pull combined with good over-rev.

Fitted with the same gearing as the 426, first gear on the 450 is only needed in the tightest of trails or steepest of hillclimbs. And with the overdrive fifth gear, Yamaha says it’ll hit 90 mph on the top end.

That bulging powerband also makes the 450 a bit more unwieldy than the 250F. It’s a bit harder to steer than the 250, especially with the engine revving high, because of the extra crank inertia. Corner exits can be exciting. Do it with too much enthusiasm and the bike runs wide because the front wheel keeps heading skyward from the pull of the meaty motor.

Do it right, however, and the beastly WR can really rail. It has the same steering geometry as the YZ model, which turned out to be the quickest-steering bike of our recent open-class 4-stroke motocross shootout. The flatter seat and tank allow a rider to get his thighs right under the handlebars, shifting the weight bias forward and helping the front tire hook into the dirt.

2003 Yamaha WR250F - 450F
Thumper power makes it hard to keep a good front end down.

Jumping off the 450 and onto the quarter-liter version shows several differences, despite the commonality of chassis, suspension and brakes. While the 450 vibrates like a mutha at high rpm, it’s barely noticeable on the 250. Novice riders will really appreciate the powerband of the little WR.

Unlike the hit of a 2-stroke bike’s engine, the 4-stroke delivers its power in a seamless rush. Yes, you will need to rev it out if you’re in a hurry, but there’s still plenty of punch off the bottom. And when there’s not, the excellent clutch allows a rider to modulate it expertly. And just like the 450, the 250’s gearbox is excellent – no clutch is necessary, up or down. 

One caveat about the engine is that it is a bit flat right off idle. The condition was a bit better once we switched to another bike, although the stumble was still present. Nothing a bit of jetting wouldn’t cure.

When the trails became tighter and more twisty, the 250 is noticeably more nimble than its big brother. The 250 is to the 450 like a 600 supersport streetbike is compared to a 1000cc V-Twin. At a claimed 233 pounds dry, the 250 is 15 pounds lighter, although the electric starting system has increased the little Thumper’s weight. We measured the lil’ WR at 249 pounds with the tank emptied.

Nice touches include the protective rear disc guard and how the left side case is notched to allow the shifter to tuck safely away in a tip-over.

2003 Yamaha WR250F - 450F
The WR250F was noticably lighter than it’s big brother and produced much less vibration at high rpms.

Suspension action is, as you’d expect, more plush than the WRs’ YZ brethren. Considering the bikes at the intro were set up to accommodate a variety of rider weights, we were generally impressed with the dampers of both WRs. The compliant suspenders suck up bumps typical of trail riding very well, although they’re soft enough that you might want to re-think taking that 60-foot triple jump at the supercross track.

Brakes are a mixed bag. The front brake is stellar, with precise modulation that lets a rider get on them hard without worry of unexpected lock-up. The rears, however, are a bit touchy on the sandy hard-pack at Hungry Valley.

So what’s not to like? Well, as much as we loved having the magic button to fire up the Thumpers, they didn’t always start immediately. We discovered that both start easier if you give the throttle a small twist before cranking it over. Further testing revealed that cold starts can require a fair bit of cranking before the engines catch fire. In this situation, we found it was better to just stand on the kickstarter and let the new auto-decompression system do its job rather than wearing out the battery. 

Two more slight nits to pick. The grips on the WR series are too hard, tearing up tired hands by the end of a long day on the trails. And, though we loved the new configuration of the seat and fuel tank, fuel capacity is down from 3.1 gallons to just 2.6. This results in a shorter range, which may bother adventurous types that love to explore for miles upon end. Still, there’s plenty enough range for hours of riding at a time.

Our overall impression of these new enduro bikes is very high. Yamaha has taken already impressive machines and made them even better. The added convenience of the electric starting system is definitely worth the slight weight penalty it incurs. Power, handling, suspension and brakes are at or near the top of the class, making the WR series highly desirable for a variety of riders, from those who want a simple playbike to full-on enduro racers.

2003 Yamaha WR250F - 450F
The WR suspension is set up plush for trail riding yet still is able to handle decent sized jumps.

Perhaps the best indication of how much we enjoyed our time on the new WRs comes from our Content Manager Ken Hutchison, owner of a 2002 WR426F.

“I’m pissed today,” he said after many miles on the new 450. “The bike was so comfortable I am kicking myself for buying the 2002 WR. I’m gonna sue Yamaha!”

Good luck on your lawsuit, Ken. Maybe you’ll get a big enough settlement to afford the $6399 for the WR450F or the $5799 for WR250F. Both models should be at dealers by the time you read this.

Kevin Duke

Contributing Editor|Articles | Bashing
A legend in the motorcycle industry, Duke Danger is known for his wheelie riding antics, excellent writing skills, appetite for press intro dinners and a propensity to wake up late. Once a fearless member of the MotoUSA team, the Canadian kid is often missed but never forgotten.