Occam's Razor: Buell XB9R Firebolt Road Test

There are certain times in a motojournalist's life when he comes across a bike that is a joy to test. The logistics are carried out without a hitch, men and machinery gel in perfect harmony, and all the riders agree-good or bad-on the outcome. At the end of the day, the story practically writes itself and our man gets home at 5:30pm, his wonderful wife ready with an ice-cold Pina Colada.

This is not one of those times.

Never before has a bike been so difficult to objectively evaluate. Never before has a bike provided such contrasting and contradictory results depending on setup, venue, and the person riding. Never before though, has there been a bike like the Buell XB9R Firebolt. A bike that marks a new direction for the American motor company, and creates a new subcategory in the sportbike world: the "Sportfighter." According to Buell, the XB is built for backroad blasting, with the occasional track day thrown in. Let's see what all the fuss is about, shall we?

We had a taste of the Firebolt at its Las Vegas introduction ("Ride 'Em Cowboy," April 2002) and that story outlines the bike's technical details and innovations. The key points, however, that differentiate the Buell from any other sportbike are these: It carries its fuel in the aluminum beam frame and its oil (for the dry sump engine) in the cast- aluminum swingarm. It also has a front rim brake dubbed ZTL, or zero torsional load. And, as much as the factory denies it, the engine is essentially a Harley-Davidson Sportster-based crankcase with two Blast! top ends-albeit with more than double the little bike's horsepower.

This is a very important bike for the company, as well as sportbike fans in general. Buell's future rests with the basic Firebolt architecture as there will be no tubular-framed models after 2002-all Buells will be based on the XB9R's general layout, although our rep in Wisconsin won't say much more than that about future models. For sportbiking, the Firebolt-if successful-could represent a change in the direction development takes. Could you imagine an R1 carrying fuel in its Deltabox frame? A CBR with two rim discs up front?

Enough! Let's ride

Jump aboard the 'Bolt and right away you'll know that this bike is totally different from any previous Buell model. The bike feels tiny, and even though the fuel-carrying frame is quite tall the bike is slim in the midsection. The reach to the bars is similar to a Japanese middleweight, even though the clip-ons are located very far forward of the triple clamp. Relative to the steering head, you sit a good couple of inches further forward than on most other sportbikes, adding to the Firebolt's forward weight bias.

No choke or fast idle, simply hit the starter and the XB fires and immediately settles into the characteristic potato-potato Buell idle, along with the associated vibes. Because the Firebolt does away with the old underslung shock (the single Showa now lives under the seat, and operates without a linkage-much like the original Yamaha monoshock setup), there is more room for the muffler, and the Firebolt is quiet without sounding strangled. The pipe's exit is right near your left foot however, and the exhaust will puff on your ankle at a stop. Footpegs are high, and the overall ergos are decidedly aggressive but not to the point of being uncomfortable.

Production Firebolts have belt guards and tensioners that are quite different from the units seen at the bike's introduction. The guard now practically encloses the belt, and the roller has a larger diameter. Both address belt longevity issues that cropped up in early testing.

The XB, while competent around town, would not be our first choice for the daily commute. The cable-operated clutch pull is somewhat heavy (and there's no lever adjuster) meaning a conscious effort is required to match engine rpm with road speed when shifting, even if the clutch is used. The V-twin has a tremendous amount of flywheel effect, and clutchless or sloppy shifting will have the bike in fits leaving a stoplight, especially in the lower gears-a hard shift will even lift the front wheel off the ground unintentionally. Although the gearbox is far superior to any previous Buell offering, it's still a stiff and notchy throw and a long way from what it should be. We know what's possible, just consider the other air-cooled, pushrod V-twin tested in this issue and how well its transmission and clutch work.

Still, once you're underway the engine has a wide spread of useable torque, and only a couple of gears are necessary around town. The bike is quite nimble in traffic, and peppy enough to have fun with. The front rim disc provides plenty of stopping power at low speeds, and the rear brake has just the right combination of power and feel. There are some low frequency, large-amplitude vibrations at lower rpms, which make the mirrors fuzzy and also seem to feed through the shock (which is mounted directly to the swingarm, which in turn bolts directly to the engine) and into the seat.

We have mixed feelings about the ZTL disc. Stopping power is excellent, but there's not much feedback. Our test unit's disc developed high spots and went totally black after a day at the track, but still worked fine.

Thanks to Buell's isolastic engine mounting system however, in which the motor is free to move in a plane parallel with the bike's wheels, vibration all but disappears above 3000 rpm. The freeway ride-with the suspension softened up a tad-is taut without being too stiff, and the engine loafs along at just 4000 rpm at 75 mph. There are some vibes in the footpegs, but the clip-ons and mirrors are uncannily smooth. Winding on the power, there are no common traits that you would expect-no airbox rush, no increased vibration, and even the exhaust note stays somewhat subdued. It's almost as if you were disconnected from the engine, with just a steady push of acceleration when you turn the throttle. And because those sensations are absent, it's easy to get carried away with the Firebolt-you have to keep a close watch on your speed at times. Wind protection is adequate for a short ride and the wind takes much of the weight off your wrists at speed, but there's a noticeable draft on your shoulders and upper torso. It's not the wind that will have you wanting to stop, however. The seat is decidedly on the hard side, and you'll be squirming about 30 minutes into a ride.

Sportfighting

Our first canyon sortie with the Firebolt had us thinking the handling was funky, for lack of a better term. With the stock suspension settings, the front-end geometry-21 degrees of rake and 84mm of trail-is so steep that the bike is reluctant to turn. It's a contradiction as aggressive geometry usually means light and quick steering, but there is more to handling than just numbers. With such a steep rake and so little trail, the forces acting on the front tire's contact patch work to turn the bars further into the direction of a turn, countersteering and forcing the bike to stand up. The situation is even worse under braking when the rake tightens up even more, and a huge amount of force is required on the bars just to hold a line in midturn.

Experimenting with the geometry by altering front and rear preload and fork-tube height, it's possible to lessen this effect significantly. However, as we made the geometry more conservative and gradually removed the bike's tendency to stand up, the steering became heavier and heavier-we couldn't find a decent compromise in a full day's riding. The situation was exacerbated by the fact that the clip-ons are so far forward of the steering stem. A good portion of any inputs made are for naught, as the bars need to turn to the side quite a bit in order to influence the steering in any way. The 'Bolt's suspension is top notch though, and the rest of the chassis feels quite stout.

While Buell has experimented with using the ZTL brake setup on the Pro Thunder bikes, Ciccotto's bike wears a standard, dual-disc arrangement with Nissin six-pot calipers. Wheels are 16.5" Marchesini cast-magnesium, and wear the latest Dunlop slicks. Engine displacement is at the class limit of 1350cc, with both a bigger bore and longer stroke than stock. The large carbon-fiber duct feeds the airbox as well as cools the rear cylinder, but is much larger than the stock piece.

In order to more easily change gearing to suit various tracks, the Hal's bike uses chain rather than belt drive. Because the bike has such a short swingarm that sits at a steep angle, chain tension varies substantially and an idler sprocket is used in place of the stock belt tensioner. Note also in this picture the braced swingarm (modified with chain adjuster) and the carbon fiber duct for air to exit from cooling the rear cylinder head.

On To The Racetrack

We segued to the Streets of Willow racetrack, which-with 16 turns stuffed into 1.8 miles-is the type of track the stubby Buell is intended for. With some sticky Metzeler Rennsports (in street compound) spooned on, the bike initially demonstrated the same traits we noticed during our canyon rides. However, with changes to the fork tube height and suspension settings, the Buell-after much experimentation-exhibited neutral steering with only the tiniest hint of a desire to stand up hard on the brakes. Why all this discussion on getting the bike dialed in? Simply this: The Firebolt is sensitive to even a two-millimeter change in fork-tube height or a quarter-turn rebound damping change. A snap judgment without careful attention to setup will lead you to the wrong conclusions about the bike.

As we expected from the street ride and from the bike's Las Vegas introduction, the rest of the chassis was well up to the task. The sticky rubber didn't faze the Buell at all, and with the geometry sorted the bike was a blast to ride. It feels much lighter than its 454-pound wet weight would lead you to believe, remains stable over rough sections of tarmac, and doesn't have enough power to get into trouble exiting turns. The front ZTL disc setup offers plenty of whoa power but has little feedback. We're certain that a normal disc setup provides much of its feedback through the hub and axle-which you feel through the fork-as it twists and flexes under braking loads. But because the rim disc is essentially disconnected from the hub, you can't feel those forces to judge how hard you are braking. The sensations from the rim disc are altogether different from a normal setup, and the closest thing we can relate them to is braking on a steep uphill-you know you can brake harder, but because it's unfamiliar territory you just don't know how much harder.

The clip-ons' forward mounting doesn't seem as noticeable on the track as on the street, and we'll theorize that because you are more hunched over when riding aggressively, your arms are at a better angle of attack to turn the bars to the side. The slimness of the bike's midsection makes it amenable to body steering, which eases the handlebar steering inputs required. The Showa fork and linkless rear shock are excellent at speed, soaking up large bumps and small ripples-and there are a lot on the Streets course-with ease. As mentioned earlier, the damping adjusters operate over a huge range, and small adjustments make big changes-all very nice stuff.

The engine's vibes are isolated from the chassis by two rubber mounts and three heim joint linkages that let the motor move in a plane parallel with the wheels. The setup works great above 3000 rpm.

On the track, Buell's DDFI injection setup with a single 45mm throttle body works flawlessly, cleanly picking up from a closed throttle no matter how many revs are showing. Power delivery from that point is smooth, but it's best to keep the tach needle near redline for best results. There's little engine braking with a closed throttle, and careful matching of the engine and road speeds is required when downshifting for smooth corner entries. It's best to upshift using the clutch too, especially exiting turns when still slightly leaned over, as the sudden lurch from a clutchless shift will unsettle the chassis quite a bit.

Back To The Street

Check out how far the clip-ons are in front of the steering stem-you sit a good couple of inches further forward relative to the steering stem than on any other sportbike.

With a better handle on the bike's setup quirks, we returned to our favorite Southern California canyons to check out the track-derived suspension settings. With the Rennsports still mounted, the bike remains neutral in midturn and steering is light. The XB still has a reluctance to turn in on the brakes, however, and in order to make time it's best to simply avoid trail braking into corners. And this leads to, shall we say, the catch-22 that is the Buell Firebolt. Tuning the chassis and appreciating its full potential requires a certain amount of savvy, and riders who are capable of doing so will almost certainly be at a level of experience where 80 horsepower is just not enough. The chassis and suspension do an admirable job-fantastic if you consider the characteristics of the engine they're around-and the bike is great fun on a tight track or twisty canyon road. However (and there's no way to sugarcoat this) if the Firebolt is to succeed as a true sportbike it really needs a smaller, lighter engine with more power. Harley has the motor-the VR1000-and Buell definitely has the chassis. Let's hope that at some time in the future the two will meet.

Test Notes: Buell XB8R Firebolt

+ Ultra-strong chassis
+ Great suspension
+ Great backroad blaster

- Extremely sensitive to setup
- Needs more power
- Geometry is too aggressive

X Our test unit was stone reliable

By The Numbers
Measuring how different the Firebolt really is

Erik Buell and friends claim some pretty outrageous specifications for their new bike, so we pulled out the tape measure and compared the Firebolt's basic measurements to more conventional bikes. Morris Ellis at Computrack Los Angeles (310/640-2825, www.gmdcomputrack.com) provided us with actual geometry numbers for the XB as well as for the Yamaha R6, and there are some substantial differences in key areas. In terms of basic geometry, the 'Bolt is far shorter and more aggressive, with three inches less wheelbase, 4.4 degrees steeper rake, and 13.5mm less trail. Important also though, are the dimensions at the rear of the bike; that tiny wheelbase is obtained by using a swingarm which is more than four inches shorter than the R6 unit and sits at a steeper angle-small changes in ride height and preload will make a big difference to the XB's squat characteristics and may also contribute to the bike's setup sensitivity. The Buell's center of gravity height is 21.6" from the ground, and the bike has 51 percent of its weight on the front wheel-both numbers on par with the open-class bikes we measured last issue. The ZTL front disc and rim setup weighs 4.5 pounds less than the R6 wheel, and the tire itself is an additional half-pound lighter than the R6's similar D207ZR Sportmax. John Bradley's, The Racing Motorcycle: A Technical Guide For Constructors (Euro Spares, 415/665-3363, www.eurospares.com) outlines a method for measuring the Moment of Inertia for wheels, and we used that process to find that the Buell and R6 front wheel assemblies have identical MoIs. The weight savings is offset by the fact that the Buell's disc is much larger in diameter, and the effective weight of the wheels-as far as aspects like acceleration and turning are concerned-are similar.

Specifications

Suggested retail price: $9995

ENGINE

• Type: Air-cooled, 4-stroke four V-twin
• Valve arrangement: OHC, 2 valves/cyl. self-adjusting
• Displacement: 984cc
• Bore x stroke: 88.9 x 79.4mm
• Compression ratio: 10:1
• Induction: DDFI fuel injection, one 45mm throttle body
• Transmission: 5-speed

CHASSIS

• Front suspension: 43mm inverted cartridge fork, 4.7 in. travel; adjustments for spring preload, compression and rebound damping
• Rear suspension: Single shock absorber, 4.7 in. travel; adjustments for spring preload, compression and rebound damping
• Front brake: six-piston caliper, 375mm inverted disc
• Rear brake: single-piston caliper, 230mm disc
• Front wheel: 3.50 x 17 in.; cast alloy
• Rear wheel: 5.50 x 17 in.; cast alloy
• Front tire: 120/70-ZR17 Dunlop D207 FY Sportmax
• Rear tire: 180/55-ZR17 Dunlop D207U Sportmax Rake/trail: 21.0 deg./3.3 in. (84mm)
• Wheelbase: 52.0 in. (1321mm)
• Seat height: 30.5 in. (775mm)
• Fuel capacity: 3.7 gal. (14L)
• Weight: 454 lb. (206kg) wet; 432 lb. (196kg) dry
• Instruments: Speedometer, tachometer, odometer/tripmeter/reserve tripmeter/clock, lights for neutral, high beam, turn signals, low oil pressure, low fuel, check engine

PERFORMANCE

• Fuel consumption: 37 to 43 mpg, 41 mpg avg.
• Quarter-mile: 11.84 sec. @ 112.5 mph (corrected)
• Roll-ons: 60-80mph/4.94 sec. 80-100mph/5.60 sec.

SR Opinions

Kent Kunitsugu

I really wanted to like the Firebolt. When I saw photos of the bike and heard about its innovative design ideas, I saw a chance for Buell to finally shed its quirky image and gain some real respect in the sportbike world. By gaining respect, I mean offering real performance compared to its peers.

Unfortunately, despite its impressive-looking design brief, the Firebolt falls short of reaching that mark. The biggest handicap is the engine; I can think of a half-dozen smaller capacity bikes-V-twin or otherwise-that would eat the Buell for lunch. And I'm not just talking outright horsepower; even the old M2 Cyclone had better midrange, and the Firebolt's real powerband is only 1500 rpm wide.

The chassis numbers would suggest a four-stroke TZ250, but the actual result is more akin to an average 600 sportbike. Although displaying excellent stability, it took some serious fiddling with the suspension and chassis ride heights before the Buell would turn comfortably, and even then it required some effort to flick into the corner. And the rim-mounted front brake works good up to a 7/10ths pace, but anything more than that and braking feel goes out the window. And why are there both metric and standard fasteners on the bike?

Buell is marketing the Firebolt as creating a new "Sportfighter" category. This might be a class I'll pass on. -Kent Kunitsugu

Steve Mikolas

Is it wrong for a sportbiker to love an American-made bike? According to most hardcore-sporters that seems to be the case, but I'm going to go out on a limb and say that I really like the Firebolt. Before I rode the new bike, Buells never made "the list" of bikes I'd want to own but that's changed now. The 'Bolt ain't for the weak of heart, or skill for that matter. It's a scrappy fireplug of a bike that begs to be ridden hard, whether it be on a closed course or your local twisties. The short wheelbase has a lot to do with its instant feedback, and makes the bike as forgiving as an ex-wife's wrath...uh...but let's not go there. When negotiating more technical terrain the rider's hard work is rewarded with a straight-shooting, no-bull design and function-now that's the American way and it seems to be popular these days-well, at least on this side of the pond. The XB9R is like no other bike and that's a significant part of its appeal. I've heard a lot of critical comments regarding the Buell but I always seem to come to the same conclusion: For what it is this bike is a keeper. That's my story and I'm sticking to it! Oh yeah, my wish list would include better brakes and more ponies. -Steve Mikolas

-Suspension settings
-Performance numbers
-Dyno chart