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/126424
- --- • 1:1 ~ t O"l t" O"l ~ C'l C'l .... tI) 6'tJ ;:j < lAbovel Warren Reid lIeftl and tuner Brian Lunnis with the Honda RC·125-79.lBelowIThe exotic Suzuki RA·125-79 is air cooled and ridden by Brian Myerscough lIeftl and wrenched on by Chris Haines lrightl. lAbovelA good look at the Kawasaki KX·125SR Uni·Trak with exposed shocks in foreground.lBelowl Jim Felt displays Yamaha"s new air cooled 125cc OW 42 works bike. Claim jumpers! 125c:c: Natianal bike. . that c:an1t be bautdht By Jim Gianatsis T he AMA claiming rule has shaped the design of factory motocross machinery in the United States. Particularly in the 125cc class where the Japanese team factory bikes have remained much more production oriented and stock appearing than their counterparts being raced in the 125cc World Championships. The trend in Grand Prix Competition this season has been towards watercooling for the rete.ntion of horsepower which can be lost by these highly tuned bikes during the course of a long 4.,5-minute moto. 18 In America, watercooling hasn't been used since 1976 by the Japanese teams for fear the tOO exotic appearing bikes would provoke some disgruntled privateer rider into utilizing the claiming rule. It hardly matters that the factory bikes are still one-off prototypes, just so long as they resembled their production counterparts from a distance. But when the claiming rule was put to misuse by a privateer who didn't even plan to race the bike he bought, the wrath of the factory teams was brought down on the AMA and they suspended the claiming rule by the following week's race. The claiming rule never should have been utilized in National Championship racing in the first place. There is a need for it on the semi-pro and qualifier level, and nothing but production machinery and related production components should be allowed in amateur racing. In the past the claiming rule has helped to keep factory bikes fairly simple in terms of their technology. Next season we can expect to see some really exotic equipment at the' Nationals with new ideas in design which have never been tried before - if the claiming rule stays off the books. It should help to make the sport a lot more exciting and interesting for everyone. Yamaha OW 42 In Europe, Team Yamaha's Gaston Rahier is racing an updated version of the original OW26 watercooled works bike which was introduced in America in 1976, winning the National Championship that year and creating the original claiming rule controversy. The engine is mounted in an all-new chassis similar to the new OW 42 being used by Broc Glover to garner his possible third consecutive 125cc National Championship. Where Broc's bike differs from Gaston's. is the engine where the magnesium OW 42 powerplant is an all-new design without provision for installation of the crankshaft driven wate.r pump as utilized by the OW 26. The new engine cases are more compact and even lighter than before. Countershaft sprocket location and swingann pivot are as close together as possible. Transmission is 6-spee.d. Only the top end of the bike is aluminum, with the piston riding in a chrome bore cylinder and fed by reed induction as is standard Yamaha works bike practice. Unlike the production F model YZS which still use monocoque backbone frames, the OW 42 utilizes an all-tube frame for cooler running of the deCarbon reservoir aluminum-bodied Yamaha Monocross shock..·· Showa air/spring works forks handle the suspension chores up front, while' travel at each end of the bike is matched at 300mm. Claimed weight for Broc's OW42 is right on the FIM limit of 176 pounds, but word has it that the bike is considerably lighter than this figure and weight will be added to it by the time anyone figures to check it. Suzuki RA·125-79 Harry Everts has clinched the 125(c World.Championship aboard a watercooled version of the new RA-125-79. The liquid is. circulated by a crankshaft driven pump through the jacketed cylinder and head 10 the front frame mounted radiator. In America, Team Suzuki riders Brian Myerscough and Mark Barnett use more conventional looking air-cooled RA-125-79 engines. Despite its conventional looks, the RA engine is- an all-new design for the. 1979 season. The steel-sleeved cylinder is a center port exhaust design with reed induction. while the production RM - 125 N still utilizes an offset exhaust port and case reed induction. The new magnesium engine case design on the RA 6-speeder has a relocated shifter shaft to prevent chllin interference, 'and the clutch actuator is moved to the left side of the engine Iilr.e on tbe bigger Suzuki bikes for more positive control. The factory RA engines use somewhat smallish 32mm Mikuni carburetors, so these little babies must be real torquers for 125s1 The reason for the center pon exhaust is the RA's new twin downtube fron! frame, similar to Yamaha's, which Honda has been trying this season as well. The twin downtube frame is supposed to offer a little more rigidity over a single downtube frame. Suspension includes Kayaba air/spring works forks up front and Kayaba deCarbon remote resevoir rear 'Shocks. Travel is 280mm at each end,