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/126244
SUZU.KI ~S ) RM.ZSB Raising the stakes in the crazy-fast I2S· motocross game By John Huetter and Gary Hymes It used to be that off-road racing bike manu- facturers devoted all their development and marketing efforts to 250 class machines. They usually offered a big bore version of the same --·i /,-.-,I ' 7.0 ,.. s.oe: RM 12S8 CHASSIS 8 bike for the 500 class and then, a lmost as an aft ert hou gh t . . . " O h , yea h . We' II also ha ve a 125 sometime th is yea r, m aybe ." It goes without saying that these days, things have changed. What used to be considered a bike for the kids has become the leading edge in motocross manufactu rers' marketing sword. There are at least two reasons. The establishment of both a National and a World 125cc Motocross Championship has given the ·sm a ll bikes a cachet of legitimacy even as it has spurred research and development efforts. Perh a ps even more important has been the youth invasion of the sport - most you ng riders start off on a 125. If they like the 125 they start with, so the factories' thinking goes , then they'll probably buy the 250 or 500 class machine of the same brand. Brand loyalty is encouraged. Suzuki grab beet' a whole bunch of new racers with their RM series 125s , particularly with the much -im p roved " A" model. They know they've got a good thing and they want to keep it. This week , they introduced the RM125 B to the motley crowd of m otojou rnalists. On pa per , the 125B offers more of everything. More torque, more peak horsepower, more suspension travel. more trick stuff, a nd more weight. It also costs more do llars , but in th e case of th e,Su zuk i you can see exa ct ly what made it cost more and why . At least some of the critical physical changes in the " B" model were proven in concept on Gaston Rahier's World Cham pionship -win nin g RA 125 works bike. Like the basic engine change of 4m m addition a l stroke to give the cylinder sq uare di mensions of 54m m X 54m m. The cylinder has all-a ro und ta ller ports with mor e radical exhaust port timing and slig htly m ilder intake porting. With the crankcase induction reed valve, it reta ins the four transfers, two boost ports and reed port to get the charge into the cylinder a nd the dual bridged exhaust port to let the burnt gases out. A new , fatter expansion chamber goes with the new motor. Horsepower peak of 21-22 ' (sprocket): HP comes at 10,750 rpm with the . torque peak around 9500 rpm. What that m ea ns is that you have to wick the hell out of the RM to get and maintain useable, winning power. O ther detail refinements in the powerplant include a faster adva ncing ignition timing curve via the electronic b lack box, a lighter piston , and larger. crank wheels. The reed valve is redesign ed to close quicker whe n there is a positive pressure to prevent bl owb ack . The Suzuki 's six -speed gearbox is the same design as in th e "A" m od el but overall gearing is taller. The carb is th e same 32mm Mikuni! with new jets. Anot her feat u re borrowed from Gaston 's bike is the suspension . No . it's not identical. You cou ldn' t afford the fo rks, let alone the bi ke , if it were . . . but it is very close . Lon gtravel spring-air combination forks were proven in the Grand Pri x bikes and tha t is what appears on the front of the new 125. T he factory air forks p rovide 9.1 inches offront wheel travel