Cycle News - Archive Issues - 1980's

~. ~ .. ~ ~ ~ ~ .... cu ..0. E cu ;> o Z Remember last year's 1987 YZ125? Well, forget. The ' 88 YZ is an all new mot orcycle and one that works. Sleek lines and a new handlebar bend make the Yamaha easier and more comfortable to ri de. Tires are Dunlops. Test: 1988 Yamaha YZ12SU Headin' straight for the top By Kit Pa lmer La tely it's been tough taking th e Yamaha YZ12 5 ser io us ly . I t 's been p lagu ed b y underpowered motors and nagging suspen sio n flaws which have kepi the YZ from being th e king of th e class, like it o nce was . . 1' 1 e 1988 \ ' Z I C)" I00 k s JUSt l ~ _J like last year's midpack run ner exce p t fo r mi nor sty ling cha nges. Swinging a leg o ver the sea t a n d tw isting the rhrott le o pen , ho wever, quick ly erases a ny n or ion that 1988's YZI25 is th e same motorcycle as last year's model. It 's n o t! All the major cha nges to the 1988 b ike are interna l. a nd th ey're cha nges tha t j ust mi ght shoot th e YZ back 10 th e fro nt of th e 125cc cla ss. Here 's w hat was done In s ide t he n ew , sa n o -Io o ki ng , silver- pai n te d (fo r me rly b la ck ) m otor are new p ortin g s pecs; a n-des ig ne d intak e man ifo ld ; a nd a modi fied Yamaha Po wer- Va lve S ySrem (YP VS). T he ex ha ust p ipe ' is 1ll'\"' , IOO . 16 T h e seve n-port mo tor feat ures a sli ghll y la rger intak e pan, a s we l l as a larger pi ston pori ree d induction sys tem . The fib er reed s are 6mm lar ger tha n th e reeds in last yea r's 125. O n th e ex ha ust port side o f the cyl inde r. th e YPVS is mou n ted 4m m low er 0 11 th e cyl inde r to a.llow for !Iew e. ha .ust-port sha pes . 1 h e va lve x Itself IS shghtl y resh aped to en ha nce ex ha us t flow. Th e pipe is a ll new to ma trh th e n e w portin g s pe~s an d . is bu i lt stronger: An a lum in um si lencer IS at tac hed to th e rear o f the pi pe a nd has more mo unting brackets. To hel p improve - u urt ub ifi ty. the new YZ ha s a large r diame ter ex ternal ro tor. T he act ua l we ig h t o f th e rot or is rh e sa me as in th e '8i YZ. h ut si nce it is larger in di a m erer , a heavier flywheel effec t is ac h ieved. Th e igniti on c urve is c ha nged 10 ra ise th e motorcycle's rev ceili ng, as wel l. T h e pr im ar y c l utrh as se m b ly receiv ed a fair a mo u n t o f uu enri on . Las t yea r's cl u tch basket p ivo ted o n a bro nze bu shin g wh ic h is no w rep laced by ro ller bea rings. Beca use of th e new ro ller bea rin gs, th e imput sha fter is 2mm la rger in di am eter. An addi tiona I fri cti on pi a re a nd cl u tc h sp ring also h a ve been added. The add ito n o f th e sp ring is design ed to g ive th e Yamaha a n even light er pull o n th e clut ch lever. Th e sixspee d transm ission is un ch anged. The bi g gest new s regardin g the Yam a ha 's chassis is the fork. Last year's unit featured Yamaha 's Va riab le Damper System, which didn 't ma ke the grade, es pecia lly when co m pa red to th e ca rt r id ge fo rks used o n the H on da a nd Suzuki rno tocro ssers. Yamaha is now the third of t he four Japanese manufa cturers to co n vert to th e proven ca rt r id ge desi gned fork s. T he 43mm Kayaba fork o n th e YZ (the Suzu kis use Ka ya ba s: Honda u ses Sh o was) gr ace 12.0 in ch es of tr a vel and are full y adj u sta ble. incl ud ing exte rna l co mpression a nd reb ound damp i ng selli ngs, I ew sea ls a re used to help eliminate suctio n . The for k produces 12 in ch es of whee l tr avel. The rear 1\lon o Cross suspe nsio n , ,i nce aga in. featu res a Yamaha-built, O h lins- type shock, bUI th ere a rc a few differen ces, th e bi ggest being th e elim ina tio n o f th e Brake Actuated Suspe n sion System, whi ch light en ed co m p n-ss io n damping when the rear brake peda l was app lied . Thi s system no lon ger ca n be used si nce th e YZ now has a n-ar d isc bra ke inst ead of a d ru m. A new va lv ing des ig n is used in the shock to redu ce o il 'frictio n a nd smoo th o u t da m p in g ac tio n . With less friction . the shoc k o il sta ys coo l long er a nd perform ance im p ro ves. The Mono Cross linkage ratios are , u nch an ged for 1988, amI rear wh eel tra ve l is up to 12.'1 in ch es. The YZ now ha s a rear di sc brak e a nd th e di sc is 220mm in di ameter, while the front di sc has g rown 10mm to 230 m m. U p front a stee l-bra ided h ydrau lic br ak e hose is used . Beca u se o f th e sw itc h to a rear disc brake, Yama ha has dropped its Z: spoke design for a more co nven tio na l straight-spok e set-u p. Yamaha feels th er e is no ad vantage in ha ving a Zspoke patter n with hubs using di sc ,

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