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/128330
TWO- po ne nts for easier e ngine starts - invo lute- type splines added to kick start and starter STROKES ratchet gear for quicke r. m or e relia ble gear engagement, plus reshaped kick-start lever for easier kick-start o pe rat ion. RM 125 Key Features Chassis: Eng ine: • Redesigned cylinder head with reduced com pression ratio for mo re stable combustion . • Revised exhau st valve timing for increased engine response at low rpm and improved traction from mid- to high rpm . • Redesigned exhaust valve gove rnor designed to complement the exhaust valve timing change and ope n the exhaust valves more gradually for a smoother, broader powerband. • New crankshaft with asymmetrical flywhe el balance similar to RM2s0 - provides improved rear w heel traction co nt rol , plus increased crankshalt inertia for better thrott le response. • New Mi kuni TMX38sS carburetor w ith power jet and throttle positi on sensor - TPS is linked to the ignition system to adjust timing to suit engine load for mor e controllable power. Chassis: • Footp eg position moved back IOmm for optimal cente r 01gravity and riding feel includes IOmm short er gear shilt lever and 13.smm shorte r rear brake pedal. RM250 Key Features Engine: • Red esigned combustion cham ber w ith reduced squish height lor improved combustio n efficiency and engine power con- trollability . • Improved cylinder port design - upper RM-Z250 co rners of main exhaust ports raised and • New titanium foo t pegs for reduced weight SHARED CHANGES [RM 125 and RM250] • New stee ring head seal cap added for improved steering head bearing protection. Updated swingarm design featuring a new bridge tube behind the pivot sect ion lor increased rigidity and improved stra ight-line performance. Improved front fork performance: • Honed inte rnal surfa ce of the inner tu be fo r smoo t he r fork m ovemen t . • Larger o il capacity above piston and shim stack for improved oil level at lull travel. • Improved dust seal. • Refined valve settin gs for better overall suspe nsion balance . • Im proved rear shock performance : • Larger inner rod for increased oil flow at full comp ression. • Refined valve settings lor better overall suspension balanc e. • Redesigned chain guide to reduce w eight. • N ew sea t cove r m ate rial fo r im proved grip, plus new seat foam for improved durability. • Smaller-sty le front brake hose 0 .0. and Allen-style brake hose bolts lor reduced we ight. • Shorter rear brake hose and hex-style brake hose bolts for reduced we ight. More compact rear brake caliper design: wider secondary scave nging ports lor • Higher rigidity for m ore consistent improved low to mid - rpm. caliper piston moveme nt and leedba ck. • Improved brake pad wear. • Revised e xhaust valve and sube xhaust valve t im ing. plus redes igned main exhaust time AMA Superbike Champ ion Mat Mladin, Ben Spies and Aaron Yates joining Pastra na for the introduction - not the com pany 's motocross regulars. H e re is a brie f loo k at these early-release 2005 models. RM-Z450 Eve r since Suzu ki released its 2s 0cc fourstroke motocross bike last yea r, the big ques tion on everyone's mind has bee n: When is it go ing to re lease a 4s 0cc fou rstroke? Suzuk i has decided that t hat time is right now. T he new bike has a totally d ifferent design fro m th e 2s 0cc four -stro ke . Some visible d iffere nces are the aluminum frame and new plastic ; howeve r, the re is mu ch mo re to th e new 450 bike than meets the eye . Th e RM-Z4s0 features an all-new,liquidcooled, titanium , four-valve 44 9cc engine fueled by a Keihin FCR40 carburetor. The Keihin has a throttle-position ing sens o r, w hich is linked to a digital COl ignitio n. The engine w ill also have a sem idry sump system featuring separa te cra nkshalt and tran smissio n o il cha mbers. In order to help save weight and add to the already compact de sign of the bike, Suzuki gave it a fourspeed transmission : Overall the bike weighs in at a claimed dry weight of 220 pounds. As for the chassis Suzuki went all out . The new frame is aluminum and is made out of a forged steering head , main spars and front mou nt bracket; extrude d rear shock mounts; and e xtruded and pressed aluminum down tubes. By using different manufacturing meth od s, Suzuki was a ble to crea te a frame tha t is stro ng but still lighter than a traditi onal steel frame . As for suspensi on : Showa takes care of that. In t he fro nt is a cartridge-style fo rk, and the rear has a Showa shock with a sOmm piston to help increase o il flow and to sta bilize t he dampin g pe rformance . Ano ther big plus for the 450 is th e fact tha t it is going to come with Re nt hal fat bars . As fo r th e other Suzu ki motocr o ss bikes , th e re are no t many changes. One impo rtan t c hange to th e RM-Z250 is larger-capacity rad iators to he lp better con tro l the e ngine temperature. The 250 and 125 two-strokes get small improvements to add to the already pr ove n bikes. Both bikes ge t improvements to the suspension and small refinements to the e ngines . The 250 got an improved cylinder po rt des ign , and the Showa suspension is refine d , as well. T he 12S got t he same suspe nsion improvements as the 250 and small changes to t he cylinde r hea d and crankshaft to help increase rear-wheel traction and t hrottle res po nse . CN • Easier brake pad maintenance. valve spring and governor spring lor improved low to mid- rpm power output • Brake pad insulator attached directly to pad to further redu ce we ight. • Hex-style rear brake pads pins for easier and response. • Refined cran kcase des ign with additional internal reinfor ce m ent ribs for added durab ility. • New crankshaft main bear ing retainer keeps main beari ngs in place when crankcase is split fo r quicker. easier maintenance. • C rankshaft inertia increased 3 percent fo r improved rea r w hee l traction con t ro l and power delivery. • New trans mission input shaft leatur ing 18 involute -type splines on clutch side, plus lighter clutch spring rate - combined leatu res pro vide light er more controllabl e clutch ope ration and feel. • Refined kick-start leve r and int ernal co m - RM250 www.cyclenews.com brake pad mai ntenance. • Rede signed rear brake disc cover w ith external mounting bo lts fo r easier ma inte- nance and redu ced weight. • New oiVair se parator added to rear maste r cylinde r lor more stable brake performance . • Master cylinder control rod threaded directly to rear brake pedal yoke eliminating lock-nut clamp system to reduce weight. • N ew alumi num handlebars . • N ew alumi num mounting spacers designed fo r easier installat ion and more secure mo unti ng rad iator shrouds. frame covers and fen ders. RM125 CYCLE NEWS • JUNE 30, 2004 27