Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
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horsepower. The ratios are staged such that when the bike is geared for 140 mph, as for Willow Springs Raceway, first gear will carry you to 75 mph . . The chassis is basically stock, bu t like the motor. there are numerous modifications and detai l changes toward im proving function. Tubular gusseting has been added to the frame at high stress locations. The swingann has been strengthened by adding tubing undern ea th the arms. The sho~~s are installed in a semi -Iaydow n posino n. Suspension is handled by KYB components. Up front is a set of KYB "Super Forks " that have had the stanchions lengthened an inch. Damping is changed by the volume and viscosity of the fluid . Springs a re normal coil plus air pressure. The shock absorbers are standard Decarbon type but the shaft can be twi sted to provide six different damping rat es. Three' sets of sp rings are available and each, set has a low rate spring. for compliance to small bumps and ,ripples, and a high rate spring to handle the big dips and ruts . Yoshimura mounts Goodyear slicks on the wide magnesium wheels . A 3.25X19 is used on the WM4XI9 Morris front wheel and a huge 3.75X18 is mounted on the spec ial Suzuki WM6X 18 rear mag . Pops used to run a Morris on th e back, but after the sprocket bolt shearing episode at Sears Point, he de cided , to use th e stronger Suzuki model. Stock d isc rotors ar e used but ar e drilled by, Pops to lighten them up a bi t. Calipers are Lockheed all a round with a Lockheed master cylinder up front and a stock Suzuki rear master. I had misconceptions at th e outset. It seemed to me that a motor putting out 130 horsepower would be peaky and hard to keep in t he powerband , thoughts left over from my sm all twostroke days . The motor that Cooley won Nationals with was not hamper ed by a narrow powerband. Quite the opposite. There is usable power from below 5 ,000 rpm and really strong from 6.000 to the 10.000 rpm shift po int. ~n fact , the motor would keep mcreasmg power beyond that but damage can result from over-revving any motor. With a powerband like that , you can divert the concentration you would use on the tachometer toward the racetrack . Like any GSIOOO , this one handles well. The day I rode it at Willow Springs, the air and track tempera tu res were very cold . All the puddles that shou ld have been water were ice! Racing slicks don 't work well until th ey are brought up to o pe r a ti ng temperature and keeping m y,body a t 98 .6° was about th e best I could do. Even so, I could see how rid eab le the bike was . On a warm da y, with hot tires and the suspension dialed in for th e weight and rid ing style of th e ind ivid ual rider , qui ck , consiste nt la p times ca n be clicked off effortlessly. After studying and riding the " Pops" Yosh imura GSIOOO , it's easy to se:e why it was the most com petitive bike a t t he Superb ike Nati onals in 1978 . • IAbove) The meanest 78 Superb ike Production racer was the Yoshimura GS1000.IBelow) Carbs were hand-mach ined t o accept smooth-bore block.