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/127206
Smoothin' Up tlle ~RM2S0 i t h the p ri ce o f m o torcycles r is ing every year, man y race rs are for ced to keep their machines for mor e than one raci ng season. Excep t for th e Pro class rider, a new mach ine every year rea lly isn' t necessary, a nd so me o f th e mo ney saved by hanging on to tha t year-o ld bike for a nothe r year or two ca n be used towards impro vin g it. Suzuki's 1989 RM 250 can easily rem a in co m pe ti tive for a t least an other year. All th e '89 mod el needs a re a few improvem ents that a n afterma rket sho p likePaul Thede's Race T ech ca n perform, improvements si mila r to wha t th e factory made to u pd at e th e mach in e for 1990. Wh en we fi rs t rode o ur 1989 Suzuk i RM 250, it was apparen t th at th e machi ne needed some help to mak e it easier to rid e. Th e stoc k RM had har sh sus pe ns io n thai tended to boun ce orr o f bumps in stead of soak them up, a nd the burst o f pow er in the midrange ma de it d ifficult to ride. It was rea lly ap pa rent whe n we ha ppen ed to bump into Paul Thede o ne day while riding a t our local track. . " T ry riding m y bike," he said. "J us t try it a nd tell me wh at you think, .. Althou gh it wasn 't a Su zuki, we th ought it was grea t. The sus pension was su per-smooth and the po wer band was th e same. Co u ld he mak e our Suzuki perform like that? It was no problem , T hede said, and at th e end of th e day he left with our bike. T hede too k the RM ba ck to Race Tech, th e sho p he has owned a nd ope ra ted fo r th e past five years. Our RM wou ld ge t T hede 's tou ch to smoo th o u t wh a t he calls a " twitchy" suspens io n, while th e mot or would get a few mo difica tions to broad en th e narrow powerba nd . In or der to smoot h o ut the suspensio n, Thede com bined the know ledge he's gained from being a former Pro-class motocrosser (Thede still Paul Thede revalved the RM 's suspension to m ak e it m uch smoother and built a powerband to match. competes in the Vet Pro class) and his educa tion th at earned him a ba chelor's degree in mechanical enginee ri ng . The stock sus pe ns io n tri es to soak up th e bumps too qu ickl y, he says, which makes it ha rsh. Thede, wh o do es a ll the valv in g a t Race Tech , revalved bo th ' th e front forks and rear shock to progr essively soa k up th e bumps. At th e front end reva lved damping rods, Spec tro Ca rtridge Fork Oil and Yam ah a 250 springs were in stalled, while the rear shock was reval ved a nd recei ved new oil. With mor e progressi ve suspens io n damping, Race T ech th en works with th e mot or in order to make all th e modifications work as a package. T hede do esn 't n ecessari ly build eng ines for peak , top-end hors epower, rather he goes for a broad power ba nd that's easy to manage. " If you can' t ge t in a nd o ut of th e tu rns quickly, who cares how fast it is do wn the straight," he says. To broad en the narro w powerband , a Moose Racing flywhee l is in stall ed to hel p improve traction. There is a n abru p t h it in th e stoc k midran ge, so tha t is cu red by mild p orting and a resh aped cylinde r head . The carb uretor is reje ue d and th e s l ide c u taway is a ltered to impro ve th rottle response, wh ile the pi pe a nd reed cage is left stock. A slo t is cut ou t o f the left side of the airbox for better ai r intake, a nd we replaced th e stoc k air filter with a Twin-Air unit from White Bros. With th e Race T ech modifications, the RM2 50 became fun to ride aga in . T he stock RM tended to W 18 (Above) The reva lved suspension makes charg ing whooped -out sect ions much easier. (Below left) A Moose Flywheel is added and t he porting altered to help broaden t he powerband and improve tract ion. (Below right) Answer's new Variable Flow Control silencer makes low-end power snappier. -