Cycle News - Archive Issues - 1980's

~ a: w ~ ..J « a.. l- ;;; e 0 z « > w ..J 0 z ll":i 00 O'l :3 > a: a: ..... :3 ~ > 0 '" C<') II) 0 ;>,. I- 0 l-o :I: a.. C'i:l = C C'i:l ~ A t alm ost $4000, the ATK 560 m ay not be f o r everybody, but it ' s got good su spension. excellent handling. (Below) Re ar end uses A -T rak Torq ue Eliminator sy stem. w hi c h reduces shock sq uat w hen the ga s is turned on. Im~ression: ATK 560 Chris Crandall's winning . h um pe r t By Larry Langley W h en a n AT K fou r-stroke ridden by Ch ris Crandall , wo n the 1984 Ba rsto w-to-Vegas H a re a n d Hound, m an y people co u ld n o t believe tha t a fou r-stroke was capable of win n in g a desert race. Sure, ma ybe four-st rokes' co u ld win a long di stance race like the Baja 1000, but not a H a re and Hound .~18 agains t the best dese rt racers i n the co untry. But th ere i t was. wi th a fu ll two m in u te lead over Scot H arden 's wat ercooled , sing le-shock 500XC Husky. T wo weeks lat er, we m et Crandall a t In d ian Dunes to ride th e ATK. Just wh at is an ATK? It 's the crea tio n of H orst Le itner, th e creator of th e ATrak T orque Eliminator, a system of drive-chain rollers th at Leitner says eli m ina tes to rq ue effects on the suspension. Leitner design ed th e ATK fra me a nd suspension a nd kept it simple. While Leitn er went to a si ng le shock setu p , he designed it to be mounted in an unconvent ional man ner, o n the left side of the swingarm . O bvio us ly th e swi n ga rm has to be extremel y beefy and rigid to with sta nd th e stress but the ide a h as been proven - BMW mounts their shock in a si mi liar m an ner (alt houg h o n th e opposite side). T h e double-d owruube, ch ro memol y fra me is built by C&J to Lei m er 's specifica tions a nd incorpora tes an o il ta n k for th e dry-sump Ro tax engi ne. T he frame and Ca l-Fab alumin u m sw i ngar m h ave a n A-Trak devi ce bu ilt in . T he engi ne is a 562cc, fo ur-val ve si n gle-cylinde r R o rax p rod ucing t . cl aim ed 47 bhp - i t is ba sicall y the sa me engine as in th e KTM a nd CanAm four-s trokes. So wha t's it like to ride ? Sw inging a leg ove r, th e cla imed 37.5 inch sea t height seem s rea sona ble - co m bined wit h th e sp ring sack caused by th e rider 's weight, th e rid er 's feet ca n to uc h th e gro und . T he AT K is su rp ri singl y co m pact for a " big " fou rstroke. Ever ything fit s. Footpe gs are mounted high which Cra ndall says keeps th e rid er 's feet ou t of th e rocks. Start ing th e 562cc Rot ax mot or is ea sier off th e bik e, kick in g wi th th e right foot a la H u sky style. T he big single ki cks th ro ugh fa irl y easi ly a nd p lacem ent of th e pi ston j us t p as t top dead cen ter is n o t as cri tica l for sta rt in g as i t is with some big-bore fourstrokes. A com p ression release is fi tted to ma ke i t eas ier to kick ove r. Once fired u p we realized how lo ud th e bike is, Th e twin exhaust p ipes funn el into a " silenc ed" megaphone whi ch lets anyone in th e a rea kn ow a booming fo ur -stroke is arou nd . A 4inc h Supertrap p is o ptional a nd we would recommen d it o n th e basis of n oise. Our firs t ea sy rid e brough t to light a jell ing g lit ch in th e 38m m Am a l car b. Th e bi ke blubbered off idl e slightly before clean in g o u t. Cra n dall har dl v n o ticed it because he rid es mosrlv w iih the thronle fu ll on. a nd one s i ~e lean er o n the p ilot je t wo u ld probabl y cle ar it up. Other than th at . 'the bik e ca r bureted clean ly and produced linear power: lo ts of it. 'T h ere didn't seem to be an y pow erband, just turn th e throttle and go . Fast. Very fast. The big thumper a te up terrain ve ry qui ckl y. Th e a bu n da nce of usuabl e power hooks upand the bik e accele ra tes. It doesn 't have th e , qui ckness o f a big twostro ke but it definitely puts th e power to th e ground. Power doesn 't mean much if th e bike doesn 't handl e bu t there the ATK sh ines. The Sh ow a front forks have 43m m tubes; a White Power shock w ith a ttached reservoir is mounted in th e rear. P roduction ATKs use a KTM front wh eel with drum brak e but Cran dall's bike has a H onda di sc brak e set-u p . H e prefers th e di sc a nd so do we - it is excellen t. Wh ile th e bike weighs more th an a big-bore two-stroke (249 Ibs. dry), th e weig h t doesn 't h in der th e handl ing tha t much . But let 's be reali st ic. T he ex tra weigh t wou ld be a ha ndicap in a reall y to u g h ra ce . Crandall is ex treme ly s tro n g (h is n ickn am e a mong the o the r racers is "a n ima l" ) an d is less bothered by the extra weight th an m os t people would be. But make no m istake. It is the best handling four-stroke we have ridden . T he unusu al (a nd si ng le) rear su spe ns io n works a nd works well, with no linkage; th e shock is easil y accessa ble. , 'The bik e is fu n to ride . It would make an excelle nt end uro bike with th e addi tio n of an odo me ter (a nd the q uieter exh a us t). It ca n be m or ocrossed and o n certa in tracks might even wo rk beuer th an a two-stroke. But it was designed as a cro ss-country ATK Engine type . .. . • .... A ir-cooled SOHC single Bo re x stroke 94 x 81 mm Displacement 562cc Compression ratio 9 .1 38mm Amal Ca rburetion Horsepower 47 bh p @ 8 0 0 0 rp m Torque •.. . ... ... .... .•. N .A. Va lves per cylinder 4 In t ake va lve size 34mm Exhaust valve size 29.5mm Intake lift 8 .8mm Exhaust lift 8 .8mm In cluded v alve ang le . • . • . " 62° Intake va lve timing .. 4 5 .5 °-7 .5 ° Exhaustvalvetiming . 74.5 °-30.5° (m easuri ng pt.) Omm Igniti o n CO l Lu bri cation Dry sump Gea r ratios Primary 2 .375 :1 (7 6 / 3 2) Fina l 3 .200 :1 (1 5 / 4 8) 5t h 0 .9 13:1 (21 / 2 3) motorcycle an d works best in that env iron me nt. The bike is extremely sta ble over h igh spe ed wh oop-dedoos a nd is co n fidence ins pi ring. We ra n it do wn a very tight ca nyo n figu ring th a t the ATK would fo u nde r like most rop -heay fou r-strokes. It d idn ' t. Jus t put yo ur wei gh t for wa rd o n th e ta nk and i t turns . Now . No t a t all lik e th e m us hy- tu rn ing manners or. sa v, a n XR500 or a T f6 00, or e ve n 'a m od i fied XR . W e w er e impressed . T o keep th e internals of th e Rotax ' eng in e clea n . a cus to m a ir box houses a K&:-': filter. The airbox o n Cran dall 's bik e was des igned for th e desert a n d. is not set up to keep water out. Modifi cations may be need ed to keep wat er o u t o f the ai r clea ner if ridden in wet co ndi tio ns . Tires used bv Crandall a t Barsto wto-Vegas were ~ 3:00 x 21 KI 39 Dunlop u p front an d a 4:50 x 18 Metzeler p ro vidi ng th e tracti on in th e rear. For o ur ride a 5:10 x 18 Dunlop was fill ed. 4th 1. 1 1 8 :1 (1 9 / 171 3rd 1.400 :1 (2 1 /1 5) 2nd 2 .000:1 (24 / 1 2) 1st 2 .909:1 (3 2 / 1 1) Rake 28° Trail .. . .. .. . . . . . . . •. . . • 4 .45 in . Front suspension . . Showa forks Fork tube diameter 43mm Front wheel travel 12 i n. Rear suspension Single Shock swingarm Rear wheel t ravel 13 i n. Front brakes .. (1) 238mm discs Rear brakes . .. . . Double leadin g shoe. 5 .1 in. Front wheel 1. 6 x 2 1 in. Rear wheel 2.5x18 in . Fronttire . 3 .00-21 Dunlop K1 39 Rear t ire . 5 .10- 16 Dunlop K490 Dry weig ht 249 Ibs. Wheelbase 58 i n. 3 .5 ga l. Fuel capacit y Ground c lea ra nce 1 3. 5 in . Seat he ig ht 37.5 i n . Retai l pr ice $3995 . .. . .

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