Cycle News - Archive Issues - 1980's

The new KX500 Kawasaki isn't a playbike, it's strictly a racer that has the capabilities to win races. It weighs 2 20 pounds dry. Test: 1985 Kawasaki KX500 The King of kings! By Kit Palmer When people think of Open class motocross motorcycles: Husqvarna, Maico (M-Star), KTM , Honda or Yamaha usuall y comes to mind first - not Kawasaki. Kawasa ki is n 't kn own for its su p re macy in th e 500cc or King (as it is known in Europe) class, but that j us t might co me to an en d in 1985. 30 Kawasaki 's j u m p back into producing a big-bore motocross ertwo years a go got off to a rocky sta rt : the new singl e-sh ock KX500 had many p ro blem s ri gh t o ff th e bat , suc h as majo r d eto n ati on a n d reli ab il it y problems. T h ings didn 't ge t a ny bet ter a yea r lat er , eithe r. Despite tr ying two spa rk plugs to elim ina te detona tion. the 500 still p inged badl y a nd co nsu mer sa les remained low . So m e thi n g had to be do ne, so Kawasaki engineers took a long look a t th e 1984 KX a nd decided to scra p it co m pl etely for a n all -new design for 1985. What the y came up with is a water-cooled, single shock wor ks replica o f Tea m Kaw asaki rider Goat Breker 's Nationa l b ike. Brek er , who fin ish ed th ird la st year in the 500cc Nationa ls, teamed u p with designers to race- deve lop th e 1985 production KX500, and th e effort seems to have paid off. Except for the co lor , there is noth ing left ove r from last yea r' s KX500. The motor has received th e most atte nt io n , th e most o bvio us being th e addition o f wat er- cooling - two ra d ia tors a re mounted forward o f, a nd slig h tly below , th e reshaped 2.5-gallon gas ta n k. The radiators, exha us t pipe and engin e a re tightl y packed toge ther, so th e exha us t p ipe m akes a radica l bend underneath and a ro u nd th e right radia to r, th en moves up a lon gside th e bike, tapers down and ha s a rebuildable a l um in u m silenc er a ttached to th e rear. The pipe ma tes with th e cylinder th ro ugh a center exh a ust port wh ere th e si ngle downtube frame splits into a doublecradle. Bore a nd stroke is sq uare a t 86 x 86mm, for an ac tual 499cc, a nd the compression ratio ha s been bumped up to 7.9: I from 6.7: I. La st yea r's 500 produced 54 horsepow er a t 6000 rpm (a t the cranks haft ); while th e 1985 p umps o ut fo ur more a t 7000 rpm - appro xima tel y 46 horsepower a t th e rear wh eel. Ma n y people who rode last year's KX complained tha t th e powerband was too explosive a n d too hard to control. T o help cure tha t problem , the ports were resha ped and a new carbureto r was used for the sa me rea son. The 1984 Kawasaki useda 38mm flat-slide Mikuni: that's been replaced by a 40m m R- bott om M ikun i with a groove machined into the bottom o f a .ro u n d slide. The groove measures 4m m deep a n d 6mm wide a nd irnproves a tom iza tio n from idle to midrange. (a ll the MX Kawa sa kis used thi s type carburetor last year except for tPp 500 .) Al so to Improve throttle response off the bottom, the KX now has a boost bott le connected int o th e rubber intake manifold; the bottle is mount ed o n th e frame's rear sub section . Insid e the inta ke cha m ber is a six pe ta l reed valve. No longer does the KX500 use two spa rk pl ugs; in stead, th e com bi nation o f ne w ' port shapes, . head design , wa ter-coo ling, ex h a us t system a nd ignition cu rve a llo ws th e use of just o ne spa rk plug wi th o u t pinging, T he a ir bo x h as a co m p letely n ew desi gn , an d it 's called th e Fresh Air Intak e System (FAIS). The box itself is huge a nd g ua rds a single eleme nt, oi led- foa m filter , but now th ere is a n air intake cham ber located underneath th e gas tank, routing cleaner a ir to th e ca rbo The design is similar to wha t m an y en d uro bikes use, but th ey usuall y funnel air down through th e frame's backbone a nd in to th e a ir bo x ; th a t wo u ld be too restrictive for th e KX. There are th ree screws holding o n th e o u ter a irbox cover, and neither th e seat o r side pa nel have to be removed to ge t to the filter. Within the large engi ne cases is a five-speed, consta nt mes h transmission a nd a wet mu lti-plate cl u tch, a nd on th e righ t si de cl u tch cover th ere is a sma ll wi ndo w to check th e transm issio n oi l level . Both th e shi ft lever a nd the kick starter are m ade o u t of a lumi n u m a lloy; the sh ift lever has a fo ldi ng tip a nd a fairl y short th row . The KX uses a C D igni tion system with a new curve, a nd a NGK B8EG sp ar k pi ug. Eve n th ough the 500 is water-cooled and doesn 't require the use of cvli nde r fins, it is still diff icult to ge t wren ch o n th e spark plug - the radiat or hose ge ts in th e way, a n d the radiat o r shrou d prevents a long th ro w of the wre nc h . T he engine si ts ins ide a n a ll- new ch ro m e-m o ly-steel fra me with a n al u mi n u m steeri ng ste m ; ra ke is steeper, 28° vs. 1984's 29°, and th e tra il is slig h tly shorte r, 4.7 in ch es vs. 4.8. In the rea r is Kawasaki 's U ni-Trak suspension wit h a si ng le , fu llyadj ustable, remote reservoir Kayaba shock. The shock has 22 rebou nd, four high-speed compression a nd 14 lo wspeed co m p ression damping adj ustments externall y located o n the reservoir a n d o n the shock body. To reduce shock fad e during lo ng motos, th e aluminum body shock has a h ea t sen siti ve co m pe nsa tor th a t restricts th e flow of da mping oi l as th e oil gets hotter. T he U n i-T ra k's rocker arm h as new dimensions, and com bined with the n ew shock's longer travel, n ow produces a less progressive suspension curve - tot a l wh eel trav el h as been sligh tly in creased fro m 12.4 to 12.8 inches. Kawasaki no longer refers to th e rear Uni -Trak stru t as being adj ustable, as it wa s originall y intended to be; unforseen strut failures have p ut an end to that. When th e KX was fi rst rel eased, o ne o f its features was th at the stru t could be adj us ted to low er or raise th e sea t h eight , which a lso changes the steeri ng a ngle to su i t th e rider 's preferen ce. T h e problem ca me when the sea t height was lowered the rea r wh eel the n h i t th e rear fend er and co ntacted the roc ker a rm when the suspensio n bottomed. That ca used so much stress o n th e stru t, ii would sn ap in half, resulting in a collapsed suspension. Now Kawasaki recommends lea ving the -strut a lone. The a onl y adva ntage having th e "adj us table" stru t is that i t ca n interchange wi th the KX250 and 125 if needed. The hefty , bo x-sec tion swi ngarm is made out o f a lumi n um and pi vo ts on two needle bearings; the roc ker arm rid es on one needl e bearing. The a ir adjustable, 43m m telescopic fo rk is a lso m ade by Kayab a an d fea tures th ree sp rin g preload a nd eigh t externa l com pression damping adjustments. The preload adjuster is located on the top of each fork leg, wh ile tile compression damping adjustment screws

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