Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/127951
1999 Kawasaki KXs cpr A B h en it co mes to the b est 1998 pr od u cti on 250cc motocro sser, Kawasaki has the lock and key to that hon or, bu t that didn' t sto p the company from tweaking on its 1999 KX250. Kawasaki felt the re was still some roo m for im proveme nts mainly decreasing we ight and in creasing power and throttle response, and focused much of its at ten tion on these areas: For the most part, Kawasaki left the hea rt of the KX250's mot or alone but di d . go after the carbureto r and ignition in search of more power . Th e Power Je t Keihin carbure tor is now s horter, so now the mai n jet, slide and the new ta pered need le o perate closer to the cylin der, thu s reducing th e amount of dista nce fu e l has to tr a v e l. A lso , Kawasaki has ad ded K-TR IC to its power- je t syste m. K-TRIC s tands for e 26 Kawasaki Th rot tle Respon sive Ignition Control, which is basically an electro nic throttle-posit ion sensor that ru ns off a . new PC ignit ion system that automatically adjusts timing wi th different throt tle settings and engine rp m. Kawasaki claims that the K-TRIC sys tem improves throt tl e resp on se and b oosts power , especially from zero to one- third thro ttle. To increase trac tion an d drive ou t of the turns, the KX250 now has a hea vier flywhee l (from 4 .5 kg-em- to 4.9 kgcm'). The rest of the engine changes were made eit he r to save weight or increase durabi lity, such as : shaving metal off th e k ickst a r t, pr imar y, clu tch an d transmission gears (to reduce rota ting m ass ); going to a ma g nes iu m clutch cover ; reducing the wa ll th ick ness of th e m uff ler en d cap; an d going t o involute s p li nes on th e co u n ters ha ft for a bette r fit o f th e co u n ters ha ft sprocket. Even the chassis has been lightened u p. The perimeter frame now has th inner wall tub ing, and th e rear subfra me is now co ns truc te d ou t of a luminum ra ther than steel. The swi ngarm has also been redesigne d in th e cas t-alumi nu m area to re duce weigh t, an d th e spoke nip p les are now aluminu m to red u ce reciprocating, unsprung weight. You might no tice fr om the phot os tha t the KX250 has a sig nifica ntly flatter profile (as does the 125, for that ma tte r).' Tha t's because the top frame spars now la y down closer to para llel with th e ground to allow a lower gas tank and flatter seating pos ition. As you can tell, the seat is, in fact, pr actically flat from fron t to back, but wha t you can' t see is th a t th e midsection is n ow narrower. Th e area of the rid er' s kn ees has a lso been mad e n arro w er , because a la rge s ec tio n of th e ra d iat or s hrou ds h a ve been cu t out to expose both sides of the fuel cell. In th e suspension d epa rtment, th e big news is th e ad d ition of hi gh - a nd lo w -sp e ed da m p ing a d juste rs , a la Ho nda. Also, some of the shock's hard ware h as been cha nged from s teel to al u m in u m to redu ce weig h t. The tri-. spring rate is unchang ed, as is the Uni- t Tra k linkage ratio; how ever, some of the ( sea ls a nd need le bearin gs have been ' r redesigned . In a nother move to re d uce weigh t,ยป the upper fork tubes are now smaller in , diameter at th e upper cla m ping area (54m m to 52mm), the same as it was in. 1996. In ternally, a new rubber bot tom-a in g d amp er has been added , a nd the fo rk b ott om in g co ne is n ow 10 m m