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/126987
a ~ New Bikes: 1988 Suzuki RM125J and RM250J . ~ Suzuki introduces new motocrossers t00 O"l ...... By Na te Rauba Photos by Kinney Jones Suzuki's bid to get back on top in the motocross wars in 1988 is spearheaded by the all-new R M250J , which was developed primarily b y Suzuki factory rider Bob replace ba ll bearings in the steering head. The backbone of the fram e is now stra igh t instead o f curved for mor e rigidity, a nd a head stay has been added. The radiators have been lowered 50m m to help low er th e center of gravi ty a nd th e mounts have been mad e stro nger. An ex tra pipe mount has been added to the frame on bo th the 125 and 250 to help red uce vib rat ion. Las t year's front stain less stee l brake di scs have been replaced by coa ted steel un its. Rear di scs are still stai nless steel. The new discs will most lik el y sho w signs of ru st after every ride, but stopping power is in creased -according to Suzuki. (The ru st is quickl y removed the fir st time th e brak es a re ap p lied). New pads are used , a nd th e rear brak e pedal has been redesigned for better feel and increased stopping power. The front brake still utilizes a rubber hos e. Suspension ch a nges on both th e 125 and 250 co me directly from the ' bikes the factory raced this year. New . com p ressio n and rebound valving improves th e front Kayaba fork s and makes th em eas ier to tu ne on both models. On th e rear o f the 250 th e Full Fl o ater linka g e has been cha nged for a more progressive rate. Rear wh eel tra vel has been in creased 6mm on th e 125, a nd th e shock sha ft is the same as wha t' s found on th e 250. Shock linkage is unch anged on the 125. Gone are the damping adjustm ent knob s on the sho ck resevoirs that cou ld be accidentally cha nged by th e rider' s boot. Now damping is adj usted by a screw on both models. H annah. Both the RMl25] a n d RM250] spor t many features that come directl y from what th e fa cto r y ra ced in 16 National a nd su percross com pe titio n in 1987. While the RM2 50 has been co m- ' pletely changed, the '88 RM125is a less radi cal departure from th e '87 machine. Both models feature new cylinders and exha us t pipes, differ ent Mikuni carb u reto rs, redesigned brak e di scs a nd modified sus pe ns io n compone nts. T he '88 RM80 is prima rily an updated mod el fro m last year's bik e. With in the RM2 50's mot or is a new version o f Su zuki 's Au tomatic Exhaust Timin g Control (AETC) system , which varies th e height of the exha us t port to match engine rpm. There are now larger stems and a new va lve design. Unl ike the valv es in last year's AETC, which slanted down a t a n a ng le across the exhaust port, the valv es in th e '88 models are fiat and run straight acr oss th e port to creat e a better seal to the piston face. New cylinder porting is designed for stronger power delivery. The new " T" shaped exhaust port has been raised, as have the transfer- ports. The cylinder itself is lined with Suzuki 'Bo ron Composite (SBC) plating instead of a conventional cast iron liner for better piston and ring wear, reduced weight and improved heat transfer. To compl em ent the porting cha nges th ere is a new exhaust pipe wi th improved ground clearance. The pipe is design ed for more horsepower and is tucked in so th at it doesn 't interfere with rider movement. Attach ed to th e end of th e pipe is a n all-n ew work s- st yl e o va l silencer th at is rebuildable. Feeding th e cylinder is the newl yd esigned 38 m m TMX fl at s lide Mikuni " Slingsho t" carburetor. The flat slide is much thinner and lighter than conventional flat slides and has a half-round indexing ridge on its face. The half-round ridge p ro vid es a smoothe r airflo w th an stra ig h t cut designs and reduces turbulence in th e carb th roa t. The result, Suzuki says , is improved th rottle response. The new design is a lso mor e sim ple and easier to wor k on so changi ng jets shou ld be faster. In th e five-speed tra ns missio n, new gea r cu tbac ks a nd polished shift for k contact surfaces are designed to mak e shiftin g easi er. Two drive and driven clutch plates ha ve been added a lo ng with new sp ri ngs for a n easy cl u tch p ull. The primary cover is now separat e from the water pump, ma king access to the clutch easie r. Fra me geome try o n the RM2 50 is co m pletel y di ffere nt. T he steeri ng head ha s been moved IOmm ou t and Im m up for better sta bili ty, wit h stadium- type w hoops i n mi n d . Ta p er ed, ca g ed ro ller bear i n gs Changes on the 1988 RM125J come directly from what the factory raced in '87. Some of the refinements are new porting, piston, pipe, carburetor, frame changes and suspension modifications. (Left) A rear disc replaces last year's drum brake on the RM125. The rear discs on both models are stainless steel; the front discs are now coated steel for better stopping power. Chain adjustment has been simplified; the 24mm axle nut loo sens t he assembly inst ead of a nut req uiri ng a 36mm socket. (Right) The RM250's motor has a new Automat ic Exha ust Timing Control (A ETC) system, porting, pipe and ca'rbureto r. Radiators have been lowered - 50 m m , and the seat- ta nk-ra di ator shroud j unction has been stream lined for easier ri der movement .