Cycle News - Archive Issues - 1990's

·: ·B IDI·N·G ~I.MPRESSION ·. - - -- - 406-CC 1994 ATK - , . ' . . ......... " ' ' . . . - - - - -- - -- - - - - -- - -- ..., T h o ug h much s m all e r than t he Japanese companies, ATK is rap idly gaining notoriety in the motorcycle world. While the 'other manufacturer s seemingly produce more models t ha n there are customers, ATK has be come known for building serious, high-performance four -stroke dirt bikes . Su re, the American company's dualsport machines are also stellar performers, bu t everyone knows that they're really justATK four-stroke dirt bikes in disguise. The fact is, ATK also produces twos tro ke motorcycles, in both 250 and 406cc displacements. Okay, that's not really a secret, but few take the Rotaxpo wered, air-cooled two-bangers very seriously. After all, the Austrian powerp lants were used exclusively by the now-defunct Can-Am company, never known for producing rockets . We loved ATK's 605 four-stroke, and were curious if the new two-strokes had enjoyed similar improvements. Still, considering the history of the ATK two-hangers . we were a bit surpri sed to get an inv ite from ATK's Frank White to take a ride on their ' 94 406 CC at the co mp an y headquarters in Utah. A trip to Utah for some trail-riding was impossible to pass up , no matter wh at bike it was on , so without further adieu, we packed our gearbags and headed to the airport. 4 AIR HAMMER As we men tioned ; the hea r t of the ATK is its Ro tax air-coo led motor , an ancient pow erplant that is about as complica ted as a bowling ball. The #406" actu ally displaces jus t 399cc, but who's counting? The engine has been around for years, and whil e it is anything but a technol og ical breakthrough, it has gained a reputat ion for being reliable thanks in part to its lack of plumbing. (A ctuall y, ATK is in the process of developing a water-cooled two-stroke motor for '95, but only a 2SOcc version is planned - at least for now.) The engine featu res a wid e-ra tio, five-speed transmission , a left-sid e kicks tarter and an electronic ignition. It is fed through a 38rnrn Mikuni flat-slide carburetor. In the chassis department, the ATK 406 features a frame nearly identical to tha t on their four-stroke mod els. In fact, it appears to us that only minimal modifications were made in order to adapt to the s m all e r two-stroke engine. Th e ex tre mely tall, powder-coated, 4130 chrome- moly steel frame has a rem ova ble s u b fr a me and a chrome-mol y swingarm. Susp ensio n is su p plie d by WP on both end s: a full-bleed 54 /57 inverted fork up fron t; a side-mounted full -b lee d single shock out ba ck . Th e shock is bolted d irectly to the swingann, and has no linkage. Like the four-strokes, the 406 uses many high-quality p arts,includ ing a Ceet se a t cove r, Talon hubs, Acerbis plastic IMS tank, Magura levers, Vimco rear brake lever, Cobra silencer, Uni air filter and 0.1.0 chain and rims. Also, ATK remains the onl y bike we krlow of to come standard with Answer's stellar Pro-Taper handlebars. Identical dual-piston Nissin brake calipers are used front and rear. That seems a little strange to us, but at least you onl y need one type of brake pads. Our test unit came with the op tional lighting kit, which includ es an Acerbis HP head light an d a brake ligh t / fen der extension. If you prefer not to spe nd the extra $195, your bike will come with an Acerb is motocross number pla te an d no fen der extension. and we ne ver experienced a bit of headshake. Part of that stability is no doubt due to the 406's towering sea t heigh t. This is one tall mo torcy cl e! The fou r -stro ke ATK that we tested earlier this year was also extr emely tall, but we figured that was due to its b ig eng in e . It makes sense. But the t w o-st ro ke e ngi ne is much smaller, so what is its excu se? Actually, the h eigh t is ra ther n ice in some respects, at least for tall riders. The seat-to-peg rela tionship is long, so the transition from sitting to standing is eas y on the knees. Also, the stability is nice at high speeds. Presently, we arrived at the mou ntain we'd been h unting, and rejoiced at AIRTIME We had two da ys in Utah to evaluate the 406, but before we could hit the trails, we had to en tertain a television crew that was do ing a piece on the ATK' factory. Of course the cameramen insisted that we repeated ly leap the bike off a large sand dune, and doing so quickly highlighted the ATK ' s mos t g la ri n g fault . The su spension - es pe cially the shock - is way too soft fo r ser ious pounding, and will bottom over even the smallest of jumps. This bike is not a motocrosser by any stretch of the imagination, and treating it as such can be a painful undertaking. After th e dune-leaping session had re d uce d us to qu iver in g shells of our former selves, we scann ed the horizon for the nearest mountain and high-tailed it fo r cover. Un fortuna tely, the only access trail was a w hooped-out, highspeed affair that had just been used in a Nation al Ha re & H ound . If you have some teeth that you 'd like to get rid of, but' are afraid to go to the dentist, try takin g a 406 on a fast, cross-graine d trail. Between the bottoming of the suspension and the vibration of the engine at high rpms, you'll soon earn a small fortune from the tooth fairy. We surrende red and backed off the throttle, avo iding the top en d of the powerband like the plagu e. The shakes aren't nearly as bad if you sh ort-shift the bike and ride in the midrange, and you can still sprin t along at a pretty good cl ip . Noth ing short of a switch to stiffer coils will cure the soft suspension. Fortunately, the trail also highli ghted a positive trait: the 406 is extremely stable. Despite the harsh bottom ing, the bike refused to twitch or d eflect to the side, which gave our tortu red nerves a little relief . The bike has a secu re feeling, (Left) No, someone did not playa joke and mount an expansion chamber on a l o ur-stroke. ATK also makes two-stroke motorcy cles, and thi s Is thei r 406.

• Cover