Thumper Heaven
Thumper Heaven
CW COMPARISON
ATK 604 vs. Honda XR628 vs. Husaberg 501 vs. Husqvarna 610
COMPARISON TESTS CAN BE CRUEL, CLINICAL THINGS. BY definition, there can only be one winner. But that
doesn’t mean the remaining finishers are losers. Case in point is this shootout of the latest big-bore four-stroke
dirtbikes. If you’re a Thumper fan, 1992 is a banner year.
Used to be that four-stroke Singles were porky. But the featherweight of this group, the Husaberg 501, weighed-in at 244 pounds, minus gasoline but with full enduro lighting. Not impressed? Well, Yamaha’s two-stroke WR500-sold without lights-weighs 258 pounds. Add a headlight and a taillight to the WR, and it would be nearly 20 pounds heavier than the Husaberg.
The next lightest bike of this group is the Husqvarna. It’s gained a few pounds this year due to numerous changes to its chassis, suspension and exhaust system, but 266 pounds dry is still reasonable for an Open-class four-stroke Single.
Only two pounds heavier, at 268, is the ATK 604. It, too, has gained a few pounds due to new bodywork, wider footpegs and thicker-walled frame tubes. Heaviest of the four bikes at 282 pounds, Honda’s XR628 is, admittedly, a potential candidate for Weight Watchers, though that hasn’t stopped it from putting in impressive race performances in the hands of U. S. Hare Scrambles and Cross-Country champ Scott Summers.
Incidentally, there’s one four-stroke Single missing from this comparison. KTM’s lightweight, but flawed, 600 D/XC wasn’t available during our test period.
Of the four bikes that were included in this test, only three were showroom stock. The XR628 is a kit bike. A Honda Power-Up Kit containing bigger-bore cylinder, piston, primary-drive gears, clutch hub, clutch springs, carburetor jets and gaskets-available from Honda dealers for $ 1000—was added to a stock $3799 XR600, giving an added 37cc and about 25 percent more power. Having these parts installed costs $200. Although the Power-Up Kit can be used with the stock XR600 muffler, a performance pipe is recommended. We installed a $300 exhaust system-headpipes, megaphone and SuperTrapp diffuser discs-from UpTite Racing (1 11 B West Dyer Rd., Santa Ana, CA 92707; 714/540-2920). So equipped, the XR628 costs approximately $5300, which puts it in the middle, pricewise, of the other bikes in this comparison.
In performance testing, the least powerful of the four bikes was the Rotax-powered ATK 604, which actually displaces 562cc. It consistently got smoked by the other Thumpers during top-speed blitzes and in acceleration comparisons. Ours was the baseline Standard model, but ATKs can be ordered with engines as powerful as a buyer desires, so more speed is easily attainable. (The 1993 ATK 604, available by early summer, will come with a full 600cc engine and a more radical camshaft.)
The fastest bike in both top speed and acceleration was H usqvarna’s mostly new 610, now being built in Italy by parent company Cagiva. Measuring 577cc, the Husky, despite being somewhat choked by large, 82-decibel dual silencers and spark arresters, convincingly won every drag-race and top-speed contest.
Only a bikelength or so behind the 610, at least up to speeds of 65-70 mph was, surprisingly, the 502cc Husaberg 501. Above that speed, the Husjky walked away from the Swedish bike. The Honda 628, showing the benefit of its added punch, also outran the Husaberg above 70 mph, although the lightweight 501 beat the XR up to that mark. Husaberg’s soon-to-be-available 600 should even the score.
As expected, all of these bikes have engines that produce a wide spread of power. The quickest, zappiest output comes from the light-flywheeled Husaberg. Engine response is comparable to that of a 500cc two-stroke Single. The Husaberg motor is always ready for a quick twist of the throttle, regardless of the speed it is turning. This revability makes for a lot of fun when riding on loamy ground or in sand, but it makes the bike more difficult to ride on hardpacked or muddy ground. Vibration is slight even though the Husaberg has no counterbalancer.
Slightly slower to rev, the 577cc Husqvarna engine behaves less like a big two-stroke, more like a big fourstroke. Heavy engine vibration (there’s no counterbalancer) is noticed at idle, but it’s much less bothersome once the bike is moving, thanks to the extra balancing effect of the primary drive gears and the clutch. Aided by a just-right amount of flywheel weight, the Husky’s engine revs quickly, yet the rear tire still hooks up well on slippery surfaces.
ATK’s 604 and Honda’s 628 exhibit the classic type of Thumper power. Both are slower to rev than the Husky and Husaberg, and each exhibits a heavy flywheel effect that allows maximum rear-tire traction, regardless of terrain or conditions. Both engines have counterbalancers, so engine vibration isn’t a problem, even when riding at speed on paved roads.
A powerful engine and a wide powerband don’t mean much, though, if a bike’s suspension and handling aren’t up to the task at hand.
Overall, every CW test rider voted the Husky 610’s Japanese-built Showa suspension a cut above the others. Fitted with a fully adjustable shock, a revised linkage and a shorter aluminum swingarm for ’92, the WXC’s rear suspension smooths small bumps well, and swallows large ones without undue bottoming.
Equally praiseworthy is an inverted fork that features huge, 45mm lower steel tubes and adjustments for compression and rebound damping.
As delivered, the Husaberg’s suspension seemed set up more for supercross than for enduros, but the upside-down White Power fork and Öhlins shock worked well after reducing compression damping at both ends. Adjusted properly, the
rear of the Husaberg was just as smooth as that of the Husky, but the fork exhibited some slow-speed harshness that couldn’t be adjusted out. Eventually, we lowered the fork-oil level by a half-inch, which helped.
Honda’s conventional Showa cartridge fork-a copy of the great 1986 CR fork-didn’t seem quite as compliant on small bumps as that of our last XR628 test bike, but it worked smoothly and progressively, and provided a high-degree of control otherwise. Fiddling with oil levels and/or oil weight should boost this fork’s plushness level up to that of the Husky Showa unit.
The XR’s fully adjustable Showa shock worked well on all surfaces.
The ATK uses White Power suspension at both ends. The 604’s fork is the same model that’s used on the Husaberg, but with heavier spring rates and different valving.
Damping and compliance are good, and low-speed harshness is less than that of the Husaberg’s fork. ATK’s single-shock rear suspension is designed to operate without linkage, which allows it to be mounted on the left side of the bike, where it’s easily accessible.
Not using a linkage system requires the use of a very stout main spring, and a different approach to rear-suspension sack. Where a normal singleshocked dirtbike requires between 3.5 and 4.0 inches of sack, the ATK gets by with 2 to 2.5 inches. This results in a taller seat height and more actual, usable compression travel.
While this linkless system works well, its range of excellence is limited: Adjusted to prohibit excessive bottoming at speed across rough terrain, the rear is harsh at slower speeds; when adjusted for smoothness at slow speeds, the rear end bottoms in high-speed gullies.
All four of these bikes have strong, trouble-free dual disc brakes, but there is a standout in the brake department, and it’s the Husky. A huge, stainless-steel rotor lives at the front of the 610, squeezed efficiently by a two-piston Nissin caliper. This brake engages smoothly and progressively, provides excellent feedback, and never requires more than a light, two-finger squeeze-even from 100-mph speeds. The rear disc, also equipped with a Nissin caliper, is just as impressive.
We had no problems with clutch slippage or grab on any of these bikes, but the amount of force that’s required to pull each bike’s hand lever varied greatly. Chalk up the Husaberg as having a clutch pull that’s lighter than that of any off-road motorcycle we’ve ridden-an 8-year-old kid could easily pull the Husaberg’s clutch lever with one finger. Just a tad stiffer in pull is the Husky clutch. After using the wonderfully easy Husaberg and Husky clutch levers, the extreme effort needed to pull in the ATK and kitted XR628 clutch levers seems absurd.
The XR and ATK, along with the Husky, don’t have to apologize for the way their transmissions shift, though. These three bikes go through their gearboxes with buttery smoothness, and neutral is only a light click away, even when stopped in gear with the engine running. Not so with the transmission on the Husaberg; it feels clunky and requires considerable force to shift. Finding neutral while stopped in gear, engine running, is impossible. Finding neutral with the engine off is possible, but it’s an extremely frustrating chore. The 501’s recalcitrant gearbox is the most obvious flaw in an otherwise wonderful motorcycle, and just shouldn’t be part of an off-road bike that costs a breathtaking $6600.
So, at the end of a four-day,' 400-mile comparison test, which one of these Thumpers is best?
By unanimous vote, it’s the Husqvarna 610WXC. Every test rider felt immediately comfortable with the Husky and praised its engine, transmission, clutch, ease of starting, suspension, brakes, styling and riding position. Want more? With a recommended retail price of $4890, the Husky is the least expensive bike in this group.
Deciding upon second place was nearly as easy. The Husaberg 50l’s light weight, quick-revving giant-killer engine, 250-like chassis feel and agile motocross-style handling set new standards for four-stroke Singles. In tight woods use, the Husaberg should have little competition, two-stroke or four-stroke. But for overall use in a variety of terrain, the Husaberg’s rock-hard seat, notchy shifting and elusive neutral cost it points.
Next comes the ATK and XR, and we’ll call that a tie. Both of these bikes were troublesome to start when cold (at least ATK offers electric starting as an extra-cost option), and always required several kicks to fire when warm-the Husky and Husaberg usually came to life in one or two prods, hot or cold. Pluses on the ATK and XR include comfortable seats, reliable engines, strong frames, good suspensions and readily available spare parts. Both are excellent motorcycles.
Losers? There’s not one here, not a bike in this foursome that our test riders wouldn’t be proud of owning. All will provide a buyer with loads of fun, whether he’s racing, trail riding or doing a little bit of both. But the Husqvarna 610 does everything just that much better, for less money. And that’s a tough combination to beat. u
ATK 604
$5695
HONDA XR628
$5300
HUSABERG 501
$6599
HUSQVARNA 610WXC
$4890
