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/127204
shorter co nnec ting rod , a modified cylinder head , port ing changes, a new boost port between the intake a nd left rear transfer port and reed valve cha nges. T he reed-va lve is moved 4mm closer to th e cylinder sleeve to reduce intak e tract length, a nd the reed -valve stoppers are modified to all ow greater valve opening. The flywheel is larger to a lmost double in ertia mass, and th e ignition advan ce cu rve is a lso altered. The exha ust p ip e ha s a lower routing, a nd th e a lu m in um silencer is an oval design a nd is sli gh tly . larger. T he radiators, gas tank and seat are mounted much low er in th e fra me (as well as the YZ1 25), a nd th e airbox is sligh tly modified for more efficient seal ing. New red handlebars are found on all th e YZS, a nd are adjustab le by moving the cla m p mou nts . . . Neither the YZSO or 490 feat ure a ny internal o r perform an ce- m inded changes for 1990. In the off-road side of the spec: trurn , Yamaha 's YZ250WR fea tu res th e exac t same cha nges as th e YZ250 MXer, however, it mai nta in s a wid eratio transmissio n a nd the heavi er flyw heel /lighting coil. Un like th e ... Other than slight cosmetic _ changes, the YZ80 is bas ically 't he same as last year's 80. It still has a flat -t op piston, a f ront disc brake and a box-section aluminum swingarm, ....... Yamaha 's new YZ490 features ~ no changes. It still has an air- cooled motor, cartridge forks and a f ive-speed t ransm ission, Yamaha has not yet released prices for any of the 1990 YZs . YZ, though, th e WR ha s reverted to th e IS-in ch rea r wheel in stead o f the 19-in ch wheels tha t are found o n th e YZI25 and 250. The sma ller diam eter rim is better su ited for off-road use. T he YZ250WR still has its whi te a nd blue color scheme, which now in cludes blue-anod ized fork sliders. ·Finall y, at! the new YZS have a special valve inserted into the gas ta nk 's vent tu be, which prevents gas from seeping out a nd soaki ng th e steering stem beari ngs. Ya ma ha ' found that the escaping gas wo uld deso lve th e grease in the bearings and red uce th e lifesp an of the bearings. • AlA SUPERBIKE CHALLENGE SEPTEMBER 1-3 These guys make MelGibson look like a sissy . They're Motor-psychos, barreling 165 MPH into hairpin turns, kaning their 1()()() cc projediles only inches from the ground, and steering with their knees. Thai's right, they steer with their knees. Reserve your tickets now and make plans to take off to Topeka . for a weekend of World-ClassSuperbike racing aI its finest. It's a littl like Daytona. A little like Laguna. And it's all right e here in the Heartland. . For more information, call 913-S62-RACE. Call for T1X a1 (816) 931-3330 or 1-800-877-1214. TIcket sales are non-refundable. . Heart1andParlc1O~J, The Center 01Amen='s Motorsporfs ~'