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/128352
By B LAKE C ON N ER PHOTOS COURTESY OF YAMAHA he R6 is without a doubt one of the most popular 600cc sportbikes ever made. However, that popularity didn't happen by accident, and Yamaha has no plans to sit around and wait for the competition to catch up. The popularity has come in part by keeping the bike fresh over the course of its seven-year history. The reason that the constant updates have been kept on the boil is that the 600cc market is one of the most competitive segments in the industry. Furthennore, despite letting the AMA Supersport title slip away to Kawasaki last season w ith Tommy Hayden, it is still the most popular race weapon in the country. This isn't just the case at the club racing level, as 5 I percent of all bikes competing in the AMA 5upersport championship were R6s, and 36 percent of the bikes on the AMA Formula Extreme grid were as well, according to Yamaha. With a brand-new Kawasaki ZX-6R on the way this year, and with Ho nda updating the C BR6ooRR, it was critical for Yamaha to make sure it didn't fall behind. The goal was to update the bike with a new inverted cartridge fork, but one change led to anot her, and the next t hing the Yamahaengineers knew they had a heavily revised motorcycle in the making. As has been the goal in this market segment for years, improving the bike's race track performance was the reaso n for the redesign . Once the can of worms was opened, three key areas were attacked: chassis/suspen sion, power output and brakes. The first area of attention was to improve the bike's chassis - this was after all what started the redesign in the first place. The bike was desperately in need of an updated front end, and with the 5upersport division getting more and more competitive every year, an inverted fork was in order. The new bike features a 41 mm , fully adjustable Kayaba unit for improved rigidity bet , ter feedbac k and better-sustained perfonnance under all conditions. Additionally, the spring rates have been increased and the compression and rebound circuits have been modified to simplify T adjustment; travel remains the same at 120mm. Another item that was changed to improve handlingand front-end feel is the profile of the fro nt t ire: The new tire is a more standard 120/70ZR17, as opposed to the 120/60 profile previously fitted . As for the rear end of the bike, changes needed to be made to balance the changes to the front . The re ar suspension's link has been changed, making the lever rat io more progressive. The vertically challenged nee d to know tha t this change increased the seat height by 10mm. The rear shoc k is similar to the unit found on last year's bike, but the spring rate was increase d and the range of adjustment was altered to Simplify adjustment. The addit ion of th e new fork was a good opportunity to follow the market trend and add radia l-mounted front bra kes . Twin four piston 5um itomo calipers are used , and despite the new mounting position, they are very similar to the excellent calipe rs Yamaha has been using for years. The brake pad material has been changed to complement the caliper change, while the master cylinder is a Brembo radial-pump typ e has been reduced from 5 to 4.5mm , saving weight while increasing performance. Although the or iginal design philosophy of near-250-like handling hasn't changed much, the new bike does have slightly more conservative geometry and dimensions . The wh ee lbase is now 5mm longer, increased from I380 to 1385mm, w hile the rake and been changed fro m 24 to 24.5 degrees and trail increased from 86 to 95mm for added stability. Handling was obviously a key to the redes ign, but power output is something that was addressed as well. The first orde r of business was to increase the diameter of the throttle bodies from 38 to 40m m. Additionally new air funnels and a retu ned , ECU (electron ic control unit) were added to optimize the throttle bodies' perfonnance. The fuel pressu re regulator now delivers fuel at 48 psi, up from 41. The result of the motor changes is a claimed 3 hp increase in power. i. www.cyclenews .com CYCLE NEWS • DECE MBER 1,2004 29