Cycle News - Archive Issues - 1970's

The new "C" model forks offer a larger air volume for increased spring rates. Th.ere have been no changes made to th~ engine. It appears Suzuki engineers felt the powerplant was potent enough In Its present state. . ting. because if yo u can bend this swingarm you shou ld have applied for the lead role in King Kong . Wheelbase is increased slightly with the new aluminum arm . from 54 .9 inches ( 1 . 395 m m) to 55 .3 inches ' (1 ,405mm), moving the little Suzuki into the full-size motocrosser specification , class . T h e longer swingaon also increases rear wheel travel a litt le bit from 8.8 inches (22 4mm) to 8.9 inches (226mm) . Rea r shocks remain Kayab a r ese voi r u nits of the deCarbo n principle and wit h t hree preload settings for the two different length single-rate springs on each shock assembly. Su zuk i adverti ses t hat the Kayabas on the new C models h ave two different dam pin g settings, but I m ust admit we never played with the adjustable fea tu re as the standard setting on the shock see med pe rfect for Ma rk's weight and mine , 160 pounds . T he spring ra tes worked pei:fectl y for us as well, but it is unfortunate that Suzu ki doesn' t offer optiona l rate - - springs fo r their RM bikes. Not all riders weigh and ride the same , making the tuning of a bike's suspension on e of the most important req uireme nts in p reparation for racing. All the factory Suzuki riders have various spring rates available for th eir works Dikes and having a properly tuned suspension on a production RM is just as important . . The front.forks are new adjustable air/spring units with tuning, of course , accomplished by altering oil volume and air pressure . The new fork assembly appears similar to th e units on the RM -250/400 , probably to keep costs down by using many of th e same parts, but travel is some 0 .7 inches 1 ( 18m m ) shorter at 9.1 inches (231mm) '1 total for the RM -125C. Less front fork travel is accomplished by using shorter dampening rods in the big-bike forks "1 to keep the front wheel tra velw ithin th e same range of travel at the rear , wheel so handling geometry isn 't upIi set. . Perfor~a ne e of the suspe~sion ' ca n only-be des cribed as excellent. It's as , .. , good as 'a nything com ing o ut ofJ apan , a nd o n Mark Barnett's Florida Se ries bi ke whi ch I ro de th e dampening cha ra cteristics a nd sp ring rat es see med perfectly su ited to th e rou gh G at er ba ck tra ck ne ar Ga inesvi lle whe re we co nd ucted our test. A nd)' m ust 'ad m it it was th e first t im e I had eve r rid den a Kayaba rear shock equipped bike that performed well on small stutter bumps and big whoops , which cert a in ly poin ts out the importance of being able to tune a sus pe nsio n system for track and riding co nd itio ns. . Aiding the rear suspension's performance going into corners while braking is a new full-floating rear brake setup. A full-floating rear brake transmits torque generated while braking with the rear wheel , directly to the frame via the torque arm where the torque is harmlessly absorbed without affecting suspension action. A no n -floating rear brake transmits rear wheel braking to rq ue directly into the rear suspension where it m ust be absorbed by the shock sp rings. adversely shorteni ng the sus pension travel and se tt ing up osci lla tio ns, m a de even worse by bumps on the ground , that produces wh eel hop . It's interesting tha t Suz uki d id n't go to the troub le of ma king the torque rod eq ual in length to the distance between th e swingarm's pivot and the rear wheel axle as required for ideal full-floating rear brake geometry . . They take the care to get the torque arm the proper length on their works bikes and it certainly cou ld n't have cost much more to do the same for the production RMs. Still , this is on ly a minor det ail that hardly affect s perfo rma nc e of th e floating rear brake since th e brake is cable o pera ted and unwanted geometry movements of the rear brake backing plate are absorbed . by the rear brake cable and not tran smitted to the brake pedal 'as a rod operated rear brake would do . Suzuki's new full -floating rear brake assemb ly can certainly be used on older RMs with just th e welding of a tab on th e frame to mount the torque rot! . The engine department remains un changed sin ce the RM -125 B m odel and it's-certa in ly a case of lea ving the best _a lo ne . Po wer comes from a ','sq u a re " e ngin e of 54.0mm X 54 ..0 mm, bore and stroke for 125cc . Compression is an actua l 8.0: I with the fuel mixture com ing from a 32m m Mikuni and rea ching the engi ne by way. of a , st rai g ht piston -timed inta ke tra ck a nd a case ind uct io n Power Reed . Gearbox is a fi-speed constant m esh unit. T he. on ly cha nge is now th ere's a lit tle knob o n th e Miku ni's pull-up m ixtu re enrich ening lever for cold starting so -magazine editors can't bitch any longer about not being able to pull it up with gloves on. In stock form the R M-125C is good enough to win . Barnett proved it by winning the first race of the Florida Series at Orlando with the engine never having been ta ken apart . By the second race in the Series mechanic ' Mark Johnson had gotten into the cylinder to clean up t he pons a bit , but port timing, carburetor and pipe rem a ined box-stock. The really ' nice thing about th e C model , besid es being p roba bly the fastest stocker in the class, is tha t it h as a very broad and usable powe rba nd . It was difficu lt to get it to bog off the powerband if you found yourself to be in the wrong ge a r at the wrong .tirne, And it's this tractability that Ma rk credits to much of his speed o n the bike a nd not just the ho rsepower. On a hilly track like Ga to rback he cou ld run a ge a r hi gher to keep up his speed while most of th e compettion found themsel ves a gear lower to keep from b ogging o n the up hill s. ' T he only thi ng I di d n' t like 'a bo ut the Suzuki was the short d istance bet; wee n the footpeg height and the seat. For m y 5'8" size it was extremely di fficult to get up into a standing position for rough sections on the track. Riders of average height or ta ller would certainly have to lower the foocpegs, increase the height of the seat , or both to m a ke the bike reall y comfortable for ra cing . Desp ite t h e big-bike suspension and wheel base, the R M125C fram e still belongs to the tiddler class. Bu t other than tha t , there's no t much anyone wou ld want to do to ch ange the new RM -125C . It 's t hat g,ood. Just in case you fee l you need m ore, a nd have the money to play with . the RM -125C can be tu rned into an eve n m o re formid able wea pon . Companies like Mot o-X Fox ha ve th e co m po nents to increase suspension travel into the 10-12 inch works bike category and in crease ho rsepo wer beyond infinite . If you 'll be campaignin g the 125 cc Nationals this su m mer that m ight e the way to go . For now , though, the Su zuki RM125C is as good as anyone could want or ne ed . Jusi ask Mark Barnett . Come to th ink of it, Mark shou ld thank us for lett ing him ri de our production bi ke . • RM-125 SPECIFICATIONS Engine Type Two-stroke. Power Reed.TM single cylinder Displacement : , . 123cc Mikuni VM32SS . Carburetor Compression Ratio ' ,. .- : . , . 8.0:1 Bore and Stroke 54.0mm x 54.0mm Star:ter System _.. _ _.. _ : Primary kick Transmission '.' . . _. _, . ._ _6-speed. constant mesh Suspension: Front Fork Air. oil-dampened• . leading axle. 9.1 in. travel Rear Swing Arm . , .. , ... Aluminum box type. gas-oil shocks, , 2 dampening adjustments. 3 load settings. 8.9 in. wheel travel Ground Clearance .. ".. .' ~ : .. , : .. (11.8 in) Brakes: Front ,., Internal expanding Rear Internal expanding. full floating TIres: Front ,,..,..,,.,, 3.00 -21-4PR. full knobby Rear , ". : .,., ·4.10-18-PR. full knobby Lubrication System """ , Fuel oil mixture Fuel Tank Capacity ." 6.3 lit. (1.7 gall Length "... . . . .. ... . .. . .• . . . . . . . .... . 2.060mm 1 81.1 in) Width , " 840mm (33.1 inl Height. ', " 1.120m m (44.1 in) Wheeibase ,. , . , .. , . , , . ', " , . , 1,405mm (55.3 in) ~ry W~ight : ,,.,,,..: " .. SS·kg. (194 Ibs) List Price $1.089 29

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