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/126264
state of fading a t which point th e air has been mixed with the o il so well that most damping is lost. This has happened in a few cases that we know of. We didn't e xpe rienc e a ny fading . Rebuilding the rnonosh ock is not possible in this co u nt ry. If you have eve r read o rh e rwi se , forg e t it unless . yo u· r.. inJapan . Yamaha Motor Corp . doesn't have the tools n ee d ed in the good old U .S .A. ye t. Because of th e ve ry nature of th e monoshock , under acceleration the YZD wa s a dream . The top 'o f the monoshock bolts to t he steering co lu m n . so under power the forc e of acceleration actually. assists in st raight line st abil ity. , The Yamaha held up well and on ly st andard maintenance was required . Withthe CO l ign ition th ere was nev er a p rob lem in sta rt in g a nd we ran the sa me plug th e e nti re time we had the rnono cr osser. W e bu r ned Yamalube a t 32: 1 an d th e piston was clean after th re e ra ces a nd severa l ph ot o sessio ns . The rea r tire on our bike was a n IR C . whic h Yam ah a te lls us will be stand a rd eq uip ment . T he fro nt was a B r id g esr o ne . Comme nts a bo ut th e fro nt ti re ra nge d fro m "fa ir" to " it does n't even begin to bi te. th e fro nt slides a ll ove r th e turns. " Afte r six motes th e rea r IRC sti ll g ave good tracti on on th e straigh ts but in th e tu r ns it was easy to te ll the knobs were worn . If you have eve r been to a Saturday Sa ddl eb ack race vou know there a rc so me prett y tri c k b ikes in t he 125 Int e rm..d iat e cl ass. Wh en th e co m p letely stoc k YZD ex ited th e first fu r n in fourth pl a ce o ur ea rl ier tho ug h ts th at th e power was indeed a d e q u a te. were verified . Mike Bell proves tha t the po wer is enough ti) win the pro cla ss by his re cord o f victories ':!n a sto ck DC 'prepared Yamaha . I When ou r novice r id e r sugge sted that the 125 YZD didn't have much ppwer d own iow or in th e co rn e rs. Bell cc u ntcred with . " It has . g ood power low in the range a nd pulls Stea dy ." Co ncerning the co rn ers , Bell sa id "j us t like any ot her 125 you don't shut o ff in the turns - just keep it wide open and use the berms to keep it on the power b~nd: ' ~ '.' r , \. : "! • ..., f I I Yamaha's emphasis on coo ling in production of the head is evid e nt in ' th e combustion chamber shape on the 125 . Counting on a cool -burning (not h igh power) dome shape, Yamaha gets away with sm all fins . If the head does overheat it leads to " p i n gi n g ' which lea ds to more heat and so on . This snowballing effect can also be caused by poor gas, wrong heat range spa rk plug, compression that is too high , ign ition riming or lean jetting. _A cy lin d e r heat offered by DC Performance Specialties gives . bencr cooling with la rg e r fins and a lso incorporates a bett e r combustion dom e sh a pe. A coo le r e n g in e, especially in the 125 class , is a fast er o ne . T he sto ck pipe works well with the engine and gives a good powerband . If th e engine . is wound pa st its peak a not iceable drop in horsepower oc curs - this is th e 125's wa y of telling th e rider to shift. Early '77 m odels had some shifting pro blems but we di d n't encou n re r a ny wit h ou r test bike evide nt ly Yamaha has taken care of tha t bug . The kick-starter o n t he bike st uc k in th e d own posit ion severa l tim es unt il it was removed a nd m oved one notch up on the sp ind le, whi ch ca use d the kick -sta rter to hit against th e cy linde r head . causing cosmet ic damage o nly. T he 125 YZD ca n win t he ju nio r class as is, Wi t h a little fine -tu n ing it ca n a lso win th e fas te r p ro classes . 1\1 ike Bell d id some tes t rid ing for Cycle N ews a nd was im p ressed with the po wer. Bell felt th e bik e pul led q ui te well in the low range fo r a 125 . The trick to rid ing th e bike fast is to become co m pletely acquaint ed wirh th e c ha racteristics o f th e rnonosh ock , whi c h handles differently tha n a ny ot he r-shoc k set-up. The powe- r pa ck age offere d is more t ha n ad eq ua te and extra power ca n be had with relatively little inv estment. Fo r a junior-cl ass ri d e r (o r belo w) th e bik e is on " of th e best offered on th e m arket . as -is. For a good intermedi at e , with a few minor c ha nges . th e YZD should be a bik e to co nside r. For the pro class . take a look at what DC's Mike Bel l is doing on a stock -powered (and we mean st ock.} rnonoshocker. ~ '" ." . • ~ .. ~ J' • • J "' ' r. • " (A bo ve left) Mike handled the Yamaha in every possible position, (Above) With the front t ire already flattened. our fork test followed a mili-second lat er. (Below ) A close look at Hannah 's 125 at Hangtown, Note the oil lines to the top of the monoshock. 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