Cycle News - Archive Issues - 1980's

tube is now sq u are-sha ped, and th e area around the swingarrn pivot is radically strengthened. The left -side rear sub-frame is now detachable for easi er access to th e shock and airbox, and the complete su b-fra me is lower to give the seat a flatter layout. The Iootpegs are mounted slightly farther rearward. Rake and trail is slightly changed. The trail is increased by 5mm to 120mm, and th e rak e is reduced 0.5° . to 27°. The swingarrn is a ll- n ew . and noticeably larger, and the old pulltype chain adjusters have been replaced by more reliable push-type adjusters. The chain guide has new a luminum side p lates and special p lastic inserts to improve wear a n d reduce Yamaha 's famous chain slap noise. The YZ comes stock wi th a 19-inch rear wheel, replacing the standard 18-inch wheel. Although the rim is o ne inch larger in diameter, the ou tside tire diameter remains the same as last year's 18-inch wheel by using a lower-profile tire. Since there is less tire sidewall compared to th e 18-inch wheel, th ere is less tire give, or b ucklin g wh en p ow ering o u t of turns, which in turn, is supposed to achieve better tract ion and m ore precise steering. . A Bridgestone 100/90-19 four-ply tire with a rather unusual knobby pattern co mes st ock on the 125. The angl ed and rectangular kn obb y pattern is designed as an intermediate, or universal , tir e - able to deliver ad equate tract ion on a variety of terrain su rfa ces. Up front is a standard 21-inch wheel with a Bridgestone , Stopping power is handled by two twin -piston caliper disc brakes , which carries sma ll clips to prevent the pads from falling out a n d rnisaligning when the wheels are removed. The rear brake ca lipe r is protected b y an all-new aluminum guard. Yamaha finall y replaced last year's awkward handleb ars with n ew Micky Dymond-bend bars , which are flatter and straighter in design. The h a n d leb a r s are now rubbermou nted. Roosting away Horsepower wasn 't a problem with last year's YZ, but suspension was. Although it handled well , it just wasn't in th e same league as th e Suzuki, Honda and Kawasaki. Bu t that's a ll changed. The new YZ has th e suspension to ba ck-up its already strong powerplant, and then some. The most im proved is the new inve rt ed fork front su spension. It has sm ooth action over the whoops, especially during the initial part of travel. Ho wever , we felt there was a harsh spot midway through the stroke. We nev er experienced hard bottoming over large jumps and it still soaked up th e smaller bum p s an d rut s without feeling stiff - a rare combination. For most ra cers the fork co mes out of th e cra te rac e ready. H eadshake is nearly nonex istent. Sometimes yo u can feel th e fro nt end twitch a little bi t in high -speed situa tio ns, but it's nothing to panic about: Although th e rear sus pensio n received onl y minor refi ne me n ts, performance is n otic eabl y better mainl y because the Monocross rea r su spension is en hanced by the superb action of the front en d. T he Kayaba shock delivers a plush ride, and lik e th e fork, rarely bottoms or swaps. The back end still feel s a little busy but not squirrelly. Overall suspe nsion performance at both ends is excelle nt. (Top) Th e new YZ1 2 5 is by far th e most comforta b le t o rid e in years. It 's muc h easier to a da pt t o a n d maneuver. (le ft) Bo t h the airbo x and airbox-to-carburetor boot are much larger in si ze t o improve breathing . Ergonom ics is m uc h improved ar's m od el. The co m biover last ye nation of the flatter sea t, reshaped h andlebars a nd bett er pl acem ent of th e Iootpegs. p rovide a much more comfortable riding position for th e rider. It is n ow much easier to move aro u n d on th e bike; you feel lik e you ' re riding o n top of th e motorcycle instead of in it. Our only co m p laint is th at we kept ca tch in g the tops of our boots o n th e bottom corner of th e seat where it stic ks down between th e side panels and gas tank on both sides of th e bike. We ended up installing a YZ490 side panel on the right side, which req u ired minor mounting bracket modifications, and rounded off th e co rn er of the seat on the left side. . The n ew ergonomics a nd chassis h as tu rn ed th e YZ into a precise turner. It cu ts a sh arp, predi ctable line through the corners without h esitation - it goes wh er e it's pointed. Little effort is needed to flick th e Yamaha in a n d out of tight hairpins, or powering through wide o pe n berms. _ Ex iting turns is one o f th e Yamaha 's s tro n g points. It tra ck s extremely well and is extremel y controllable. Yamaha claims this is accomplished by a combination of Yamaha YZ125W Engine type Liquid-cooled. two-stroke. single 56.0 x 50.7mm Bore x stroke Displacement 124.Bcc 8 .8 /11.0 :1 Compression ratio Carburetor 35mm Mikuni NI A Horsepower Torque N/A Starting system Primary kick Ignition , COl Lubrication Premix Primary drive Straight-cut gear Final drive : #520 chain Frame Single downtube. split double cradle 27° Rake Trail 4.72 in. Front suspension Kayaba inverted telescopic fork 41 mm Fork tube diameter Fron t wheel travel. 11 .8 Rear suspension Kayaba Monoshock. swingarm Rear wheel travel 12.0 Fron t brakes Disc Rear brakes Disc Fron t tire 80/100 Bridgestone M51 Rear t ire 100/90 -19 Bridgestone M59 Claimed wet weight 192.0 Ibs Overall length 84.1 in. Overall width 33.5 in. Overall height 49 .0 in. 57.1 in. Wheelbase Fuel capacity 2.11 gal. ~ .14.0 in. Ground clearance Seat height 37.2 in. Retail price $3149 thi ngs, such as the bigger rea r wheel, n ew fram e a nd smoothe r power o ut pu t. What ever the reason - it works. T he rear Bridgesrone tire performs su rp risi ngly well , m uc h bett er th an we though t it wou ld. Even on th e driest, hardest-p acked tra ck we co u ld fi n d , th e rear tir e hooked up ade quately. Even af ter many hours on the tra ck th e tire shows little wear. So, until aftermarket 19-in ch tires become readily available, th e stoc k tire will suffice. The front ti re digs in well , too. The YZ's m otor d eliver s good power, noticeably m ore than last year 's, but some bottom-end punch wa s sacrificed. When the YZ comes o n th e pipe, slightly later than th e '88 model, it pulls long and hard in a smooth manner. Mid-range is where most of th e h orsepower in crease "is felt. Even though some bottom-end g ru nt was lo st it still h a s en ou gh torque left over to keep m ost riders h appy, including us . It still pulls strong exiti n g tu rns and a quick fan o f th e cl u tch helps for even qu icker getaways. One finger on th e lever is more than enough to ge t the job done. Shifting gave us no hint of troubl es. A slight tap on th e lever is all th at 's needed to find th e next gear a nd missed shi fts were few an d far be twee n. O ff the track, the Yamaha is easy to m aintain. Access to the a ir filter is from th e top after removi ng the sea t, but we recom me nd unbolting th e co m p lete a irbox unit when servicing the filter. The way th e filter is positioned it's very easy for d irt to fall into the carburetor, no ma tter h ow ca refu l yo u are. It means a few more bolts to remove but th e ben efit co u ld save yo u big-tim e in th e long run. Chain adj us tme nt is simple with the new push-type adj us ters a nd th e cl u tc h a sse m b ly can b e reached without having to rem ove th e entire clutch cover. Last chapter The 1989 YZ is th e best 125cc MXer Yamaha has produced in years. It has th e power to get th e job done and finally has th e susp ension to keep up; but we have o ur do ubts ab ou t th e 19-inch rea r wheel. Tire selecti on is go ing to be limi ted for awhi le a nd th e ri sk of pinch ed in ner tu bes is going to be gr eater with the lower p r ofile si de wa ll t ir e. H ow ever, throughout our testi ng of th e YZ, we exp er ienc ed no flats . Other than th at we have no real co mpla in ts with the new YZ - just p ra ise. Yamaha sho u ld be proud. • like the b igger YZ250. the 125 fe a t u re s a 19-inch rear wheel. The benefit is le s s sidewall movement for better contro l in the turns. -

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