Cycle News - Archive Issues - 1980's

~ ~ . :;--C LC') 00 O'l ~ ~ (,Q .... v ..0 8 v ;> 0 z (Above) Yamaha's 1986 TZ250 race bike . (Below) Details of the TZR250 street b ik e ' s sw i n g a rm and rear suspension . Note hollow-spoke wheels . Race bikelstreet bike: Yamaha TZR250 By J ohn Nutting Yamaha 's new 120 mph 250cc sports bike was launched in Tokyo recentl y a n d i t's the closest sports riders w ill get to buying a facto ry racer in road trim . For the new TZR250 was deve loped in parallel with th e latest TZ250 race machin e bv . th e sam e team . 22 Grand Pr ix bike engineer. Xl r, Abe. has in corporat ed man y of the sa me • co m po nen ts from th e racer in to th e TZR250. And th a t incl ud es th e lig ht -all o y beam fra me . super-light 17·in ch th ree spoke holl ow wheels and massive fro n t brak e. T he T ZR 's engine is a co mp letelynew pa ra lle l twin wit h reed -in d uctio n into th e cra n kcases th at is cla im ed to boost the mi d ran ge to rque. T he la you t is identical to th at used o n th e 500cc grand prix \' -Iour and internal dimen sio ns a re th e sa m e as th e RD 500 L Cs a t 56.4 x50m m . to gin- a ca pac i ty of 249cc. Separate cylinders are used , givi ng mo re room for up-to-date tran sfer p orting. T hese are fed by n ew fib er reeds and [lat -sl ide 28rnm I\likuni carburet o rs . As o n ti lt' cu rre n t RZ250RR made in japan , exha ust po wer val ves bro aden th e power ban d . But even so, th e cla imed peak power is sti ll 45 bhp at 9500 rpm . th e j apan est' ind ustry's ag reed limit for th e 250cc hom e ma rket. It 's likely th ai ex po rt markets wi ll be served bv model s wi th up to 60 bh p o n tap. so me 10 bhp down o n the race version. As o n the racer . th e six-speed gearbox is lu brica ted by a pum p in the p rim a ry ca se driven from the cra n kshaft. A new tw ist in engi ne lubrica tion is th at the au to lu be p um p is co n troll ed by revs, th rott le open in g a nd now by th e pow er-val ve open ing. Rubber engi ne mounts a re used to support th e un i t, o ne at eac h end . But th ey are posit io ned so th at the engi ne 's (Above) The TZR250 street bike, as sold in Japan; no plans exist for U.S. sales. (Below) The T ZR250's intake and exhaust tracts. center o f gravity is between th em for best a bso rp tio n of th e vibration. Chassis is right up to date with th e fro nt fork offerin g a ir a nd prel oad adj us tme nt while a t th e rear a si ng le m onosh ock unit is used. Wh eels are 17-inch aga in as o n th e racer, but have Marvic-style threespoke hollow wheel s. Brakes have a su perb spec with a flo at in g 12.6-inch di sc and a Brernbo-type doubl e pi ston ca lipe r. Rear di sc is a tiny 8.3in ch unit. Dr y wei gh t . o f th e TZR250 is 10 pounds less th an th e Suzuki 250 G amma a t 277 pounds. Yamaha is pl anning to prod uce 15.000 TZR250s in addi tio n to th e RZ250RR in a bid to make th e bike • th e top seller in japan . Yamaha TZR250 Engine type ••••. Water-cool ed. two-stroke, reed-valve. powervalve parallel-twin Bore x stroke . • • • . •56 .4 x 50m m Displacement . .. .. .•. . . 249cc Compression ratio • . • . . .. 6 .4:1 Carburetion • . • .. @ 28mm flat slide Mikuni Hor sepow er 45 bhp @ 9500 rpm Torqu e .... •.... . 25 .3 lb. -ft. @ 9000 rpm Starting system .. . ... . • ... Kick 12V 5A H Battery rating Igni tio n .. . . .. .•. • . .. . . . . . CO l Injection Lubric ation Re dline . ... . •. .... 10,000 rpm Rpm @ 60 mph 5100 rpm Primary drive Helical gea r Final drive .. •. •.. .. . • .. Chain Gear ratios Primary • • . .• . . 56 /22 ; 2 .55:1 Final . .•.. . . .. 4 1 / 14 ; 2.93:1 6th . •.. .. . . .. .... . . . .0.B5:1 5th .. .. . . . . .. .. . . •. . •0 .96:1 4th . . . .. . • • • . . , 1. 0 8 :1 3rd •. • . • . ••••. •. .•... 1 .32:1 2nd 1 .75:1 1 st .. . •. . . . . . • . .... .. •2 .46: 1 Calculated speed in gears at redline 6th •. .•. •.• . .• •.•• . 11 7 mph 5 th . . .•. •.•. • . •.•.. 1 0 3 mph 4 t h ... •.•.. •. • • • •. • . 92 m ph 3rd . •. •. •. ••.. •. •.. . 7 5 mph 2nd • •. •. •. • • . .•..•. • 57 mph 1st .. . .• . •• •. . . ..• .• . 40 mph Frame • . . Box-section aluminum alloy Rake ... . . • .•. . .• . •. .. . . . 26 ° Trai l 3 .8 in. Front suspension type Telescopic forks Fork tube diameter 39mm Rear suspension type .• . Singleshock swingarm Front brake .. .. . 1 2. 6-inch disc Rear brake . • . . . .. 8 .3-inch disc Front wheel • .. . Cast aluminum alloy Rear wheel .• . .. Cast-aluminum alloy Front tire 100 /80-17 Rear tire . .. • • • •. .. 120 / 80-17 Claimed dry weight • . . 277 Ibs . Claimed wet weight . .. 31 2 Ibs . Overall length •.. . .. . . . • 7 9 in . Overall w i dt h . . . . . . . . • . . 26 in . Overall height 4 4 .7 in . Wheelbase . . • . . . . . . . . . . 54 in . Fuel ca pacity . . . . • • . . • . 4 .2 gal . Ground clearance . .. • • •. 5.3 in. Seat height . • .. •. . . • ... 30 in. Colors ••. . • ••. •• .. . Red / w hite

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