CRF250X Development

Take a new-generation motocrosser--then add the good stuff to create an awesome off-road racer.

Pedigree counts. Check out the new 2004 Honda CRF250X, and your eyes quickly detect all the fundamental genomes shared by the 250X and Honda's spectacular 2004 CRF250R motocross machine: fourth-generation aluminum frame, ultra-trick four-valve 249cc Unicam® engine, 47mm Showa twin-chamber fork and Pro-Link single-shock rear suspension with a racing-style aluminum swingarm, dual disc brakes, even an aluminum Renthal handlebar--it's all there. Call the two bikes fraternal twins and you'll be right on the money.

But understand that when you're developing a world-class high-performance off-road bike, beginning with a world-class motocross machine merely makes for a good starting point--with much more work still to be done. After all, motocross courses never contain miles of rock-strewn single-track paths zigzagging through trees, over roots and across streams. And you'll be hard-pressed to find a GNCC course, desert route or enduro course studded with triple jumps. Which is to say, the specific design goals differ radically between a motocrosser and an off-road bike, so if you're going to build a world-class machine, these particulars must be addressed.

Charting the changes

Even though the rolling chassis and the engine in the X-model follow the exact same architecture found in the CRF250R, many brand-new elements set the CRF250X apart--changes that make it uniquely equipped to fulfill its specific target function. The list of major changes includes:

  • A new camshaft for a wider powerband and increased torque
  • Wide-ratio gearbox for more versatility in varying terrain
  • Added flywheel weight for more tractable power delivery
  • New exhaust system, complete with spark arrestor
  • Larger fuel tank for greater range
  • Electric starter, battery and ACG--plus a backup kickstarter
  • New frame tuned specifically for off-road work, not motocross tracks
  • More compliant suspension components front and rear for a plush ride over rocks and roots
  • Revised linkage ratios for the Pro-Link rear suspension system
  • An 18-inch rear wheel and tire for added flat-tire resistance
  • A new lightweight slim-line headlight, plus a trick LED taillight
  • Standard-issue sidestand
  • California model meets Green Sticker eligibility requirements

Considering this is just the brief list, it obviously represents substantial changes indeed. And this list is only half of the story.

The road to a new machine

Knowing that off-road competitors would spare the CRF250X no punishment, Honda's engineers scoured the entire United States in search of the roughest and tightest competition-grade single-track trails. Diverse locations including riding areas in New Hampshire, Texas and Georgia, plus a big Midwest tour provided the hands-on proving grounds for building the ultimate high-performance off-road machine. This was the most thorough real-world prototype-testing regimen Honda had ever conducted for an off-road machine, but the knowledge gained proved invaluable to the CRF250X development process.

Although the CRF250X development program began with a machine that was virtually a "motocrosser with lights," it soon became apparent such a machine was simply not the ideal configuration for meeting the needs of top-rank off-road riders. Indeed, it would have been much easier and faster to throw a headlight and taillight on the CRF250R and call it a day--but that's not the Honda way.

Built to withstand the enormous loads associated with triple-jump-infested Supercross tracks and fast outdoor motocross courses, a motocross-style rolling chassis--frame and suspension components--is just too stiff for the off-road world. Here, the tight, technical and rough trails competitors typically encounter demand a bike designed for bump absorption of a different kind, characteristics aimed more at soaking up smaller and more numerous irregularities rather than coping with huge, bone-jarring 30-foot-high landings. The thorough testing regimen conducted by Honda's development engineers revealed that a motocross-style chassis created too much bump impact during off-road use, which hindered steering accuracy and inflicted undue fatigue upon the rider.

A chassis tuned for off-road competition

To meet off-road requirements, Honda's development team created a whole new frame for the CRF250X--albeit one with differences nearly invisible to the naked eye. The central downtube area, engine cradle and engine mounts all changed in thickness and shape, and new swingarm pivot plates also give different rigidity/flex characteristics compared to the frame used in the CRF250R. Although subtle in appearance, these changes drastically alter the bump absorption, tracking and turning characteristics of the frame to fit off-road-specific needs.

In addition, the CRF-X development team altered the suspension components at both ends, tailoring them specifically for off-road applications. Again, although subtle in appearance, changes to the taper machined into the fork tubes--a new two-step taper plus a cutaway 20mm longer--allow the fork to react in a more compliant manner to small, sharp-edged bumps. Softer fork springs and lighter compression damping rates also add a significant degree of plushness to the CRF250X's fork action.

Honda engineers also altered the Showa Pro-Link single-shock rear suspension system in like manner. A new, less-progressive linkage helps create a more compliant ride throughout the entire range of rear-end travel, and a softer spring and lighter compression damping settings allow the rear end to swallow up the myriad small bumps and dips encountered out on the trail. Even though the untrained eye will see only a sidestand to distinguish the CRF250X chassis from the motocrosser's, these extensive revisions create a new machine eminently qualified for the task at hand.

An engine that's lean, mean and green

Compared to motocross racers, top-level off-road competitors encounter an incredible variety of terrain during the course of an event, including sections closer to a trials course than a motocross track. As a result, sheer peak horsepower gives way to a torque-laden engine with a wide, tractable power delivery and a wide-ratio gearbox. To these ends, the development team once again began with Honda's lightweight new-generation CRF250R Unicam four-valve powerplant, then adapted it specifically to fulfill off-road priorities. The overall engine architecture remains unchanged, as do many key components, such as a 78mm slipper-type piston with a compression ratio of 12.5:1, Nikasil® cylinder liner, plus lightweight 31mm titanium intake valves and heat-resistant 26mm Inconel® exhaust valves.

A new camshaft designed for off-road-style power output replaces the high-rpm motocross cam of the R-model. The X shares the R's 37mm Keihin flat-slide carburetor with throttle position sensor (TPS), albeit with new jetting specs better suited to its intended use, and a longer, easy-to-adjust air screw. To give the 250X a more tractable power delivery, Honda's engineers also added more mass to the flywheel, all the better for low-speed slogging through really tough terrain. A new primary gear pairing, new final-drive sprockets and a revised five-speed gearbox with wider gear ratios also make the CRF250X better suited for serious off-road work. In addition, there's a new exhaust system tuned specifically for off-road use, and it's capped off by a USDA-qualified muffler/spark arrestor.

As emissions requirements for off-road vehicles grow ever more restrictive throughout the U.S.A., manufacturers become hard-pressed to find a balance between on-the-trail performance and environmental responsibility. However, with the CRF250X, Honda's engineers deliver a potent package that also meets all EPA standards for 49-state bikes, plus a separate California model that meets the California Air Resources Board (CARB) requirements for the Golden State's coveted Green-Sticker status right off the showroom floor--a lofty achievement indeed, one that will be welcomed by thousands of West Coast riders.

Class-A additions for a first-class machine

Anyone who has spent hours in the saddle competing in off-road events knows that the small details add up to big differences by the end of the day. That's why the CRF250X is endowed with a wealth of smart-think touches, beginning with an electric starter, plus a kickstart lever complete with automatic decompressor system for backup use. The clutch now includes a coned-disc spring for better feel and smooth engagement. An 18-inch rear wheel and tire come standard, providing superior ride comfort and compliance. A new T-ring-sealed final drive chain is narrow, stronger and lighter than conventional chains. The CRF250X also features a new side-access airbox that allows quick and easy filter servicing with no tools.

In deference to its off-road agenda, the 250X gains range thanks to a larger, 2.2-gallon fuel tank. Compared to the R model, the seat is wider and made of different density foam designed for long-range comfort. Even the aluminum Renthal handlebar contributes to rider comfort by passing less vibration on to the rider. Another off-road addition is the second engine-guard, added for more protection without the mud-gathering tendencies of a full skidplate. A new-design 35-watt halogen headlight pumps out plenty of illumination after dark, and a new-design LED taillight has been integrated into the rear fender. As would be expected, an easy-to-read, resettable three-digit competition-style odometer is also part of the CRF-X package.

Imagine, if you will, a world-class specialty shop with nearly unlimited resources, one that will take the latest, hottest motocross bike and add a long list of specialty parts that add up to the ultimate high-performance off-road bike. That's what you have in the 2004 CRF250X. And the name of that wondrous shop? None other than Honda R&D.