Cycle News - Archive Issues - 1980's

The f ront brake's actuating arm is mounted behind t he backing plate. Test: TY350 Yamaha Yamaha's trick new trialer By Kit Palmer It's been eight long years since we 've last seen a TY Yamaha, or any Japanese trialer, imported into the U.S.; but now Yamaha has ended that dry spell by introducing an a ll- new tri al er. Yam aha unveiled th e latest hi-tech , single s hoc k T Y25 0 la st yea r in Eu rope, a n d it met wi th huge 18 success. T ha t Eu ro -market a lso sparked interest in th e U.S ., a nd rrial er s a ll across th e co un try tri ed to ge t th eir hands on a TY - few were successfull. But indications o f demand were strong enough to a ttrac t Yamaha Mot or Corp . U.S.A ,'s a tten tion . Tria ls even ts in th e U.S. don 't ha ve Europe's 250cc limit, so Yam aha deci ded to bu ild a nd import th e T Y350. Besides th e larger displacem ent, th e 35 0 features som e n ew i nte r na l cha nges , suc h as larger cra n k halves to help g ive th e TY a stro nge r and smoothe r torque curve. Th ey ar e th e same size as used on th e YZ490 rnorocrossers, and increase th e flywheel effec t, red ucing th e cha nce of sta IIing th e mo tor wh en pi on king aro und a t slow speeds. This vear, th e TY uses a ch ro mebo re cylin der for better coo ling a nd light weight. Si nce tri al s is a slowmovi ng sport, th ere isn 't a lot of cooling ai r ci rcu la ting through th e cylin der fin s, so th e im proved heat transfer provided by th e chro me bart' (vs. a n iron liner ) is appreciated. The en gine has a n 80 x 86mm bore a nd stro ke, a low 5.3: I compressi on ratio, a nd actual displacement of 34 Icc. Carburetion is handl ed by a 26mm T eikei feeding into a four-petal reedvalve induction manifold , Th ere is a pull-type choke knob m ounted o n th e left side of th e car b; an o iledfoamed a ir filt er is surrounded bv a pl asti c airbox. (So me people. keeping in mind th e chrome-bore cylinder. worry that th e a ir filter is too porous a nd should be replaced by a denser foam filter; if an y dirt finds its way to th e cylinde r. it can eas ily destroy the ch ro me lin er, and cylind ers with ch ro me liners can 't be rebored ). Reaching th e filt er is si m p le, just pop th e center/sea t section o ff; no to ol s a re necessarv. Yamaha made th e filt er easy to gel to so th at o n- thetrail service ca n be done in a few qui ck minutes, just in case th e bik e ever gets su bme rged a nd fill s th e a irbox with wat er. The exha us t pipe joins th e cylinde r th rough a side-po rt exha us t manifold, cl imbs p ar all el to th e frame's front downtube, a nd is tucked in close to th e cylinde r. reducing th e chance of damage co ns ide ra bly. It winds its wa y over th e cylinder head and a lo ng th e left side of th e bike, a nd a t th e en d o f the p ip e is a n a lu mi n u m silencer th at is not U,5, Forest ry-appro ved . T he TY ha s vour basic wet mult idisc cl u tc h a n d 'a six-speed tra ns m iss io n . First throu gh third g ears, th ough. are design ed to have a lmos t zero backl ash - th e tran smi ssion dogs fit tightl y, resulting in less jerk y, more precise and more con tro lla ble pow er delivery in slo w situa tion s. Th e rest of th e gea rs have norm a l backlash . A l1520 D.LD . cha in run s through a new, stro nger pl asti c cha in guide a nd wraps aro und a 12-tooth co u n tershaft an d a 42-tooth rear sprocket. Bo th right a nd left engine side co vers are m agn esium, a n d th e right side clu tch cover is tapered from th e cl u tch co ver housin g to th e fro nt o f th e engine, so th e housin g won 't ge t h ung up o n roc ks; th at a lmos t eli mi nat es the cha nce of sm as h ing th e intern al clutch ba sket , or ca us ing th e ri der to dab. A sturdy a lu m in u m ski d p la te gu ards th e lower engi ne cases an d Ira rrie, a nd forms arou nd th e low er p ortion o f th e engine side cases. The Yamaha has a CD igniti on system and flywh eel magn eto ge nerator; th ere's a six- volt headlight and taill ight. The high-tensil e steel frame has a single front downtube th at sp lits halfway down into a doubl e crad le. Rak e is a steep 23°. and trail is 1.93 in ches. Wheelba se is a short 52 in ch es, seat height just 29.3 in ch es, and ground cl earance 12.8 in ches. One of th e mo st unique features of th e TY is its sing le-shock rear su spen sion , whi ch is ver y similar in design to th at found on th e Yamaha YZ morocros sers . Currentl y th t'TY is o ne o f only two sing le-s hoc k tria lers in producti on - th e other is the n ew Beta , but Honda now has a single shoc ker in th e works a nd will prob- ably be seen on ly in Europe, There are six pivot points o n the TY 's Monocross linkage system and four of them hav e zerk fillings . The conglomerat e of linkages a n d levers produces 6,3 in ch es' of rear wheel trav el. but th e short 12.5-inch Yamaha -built, DeCarbon , nitrogen ga sfill ed sh ock uses on ly 2.2 in ch es of strok e. It has three preload adj ustm ents a nd no internal or externa l co m p ression o r rebound dampi ng se tt in gs . Th e swingarm , like th e fram e, is mad e o f high-tensile steel ; th e kickstand is bolted to th e swinga rm on th e right side. U p front is a Kayaba fork wi th 36m m sta nc h io n rubes a n d 7.1 inches of wh eel travel; there a re no protector s on th e sta nc h io n tubes or fork sliders. Mounted to the right fork leg is a n od om eter/ speedometer unit. Both front a nd rear gold-anodized rims are laced by Yamah a 's excl us ive Z-spok e design , a nd th e tir es a re made by Michelin. Drum brakes a re used a t both en ds: th e front brake actuating a rm is mounted in sid e the magnesium backin g plate out of harm's way from rocks , The fenders, fuel tank, cent er/ sea t secti on and headlight co wling are made o u t of stur dy, white plastic. Other features include ch ro me hand lebars; smooth, black grips; a fo ld ing sh ifrlever an d a 120-page owner' s m anual. The bike wei gh s 196 pounds drv . ki ck sta rt in g th e TY is not easy it takes a go od healthy sta b a t the lever to turn over th e engine. With th e choke kn ob ra ised a nd n o throttle, a co ld engine would usuall y fire bv th e fourth kick, Beca use o f the 1"Y's relativel y low sea t height co m pared to its kickstart lever , the best wa y to ge t goi ng is for th e ride r to jump up a n d th en bring his full wei ght down o n it. With clutch disengaged, in -gear sta rts a re possible. This Yam ah a ha s torque, a n d a lot o f it. No rnauer how low in th e rpm range, o ne quick wack of th e throttle will make th e TY jump forw ard very smoothly and pr edictably. The engine responds cleanl y a nd accurat ely whenever th e throttle is twi sted - it never hesitates wh en the going gets tough. Sometimes, though, when the bike gets dropped on its side a nd th e motor dies , it's di fficult to restart because the bike loads up. Kicking though with th e thrott le wide open will make it restart, blurb and cough for a few seconds. then clear out. The clutch is easy to use when need ed and has a light, one-finger pull. When the clutch needs to be feathered , it isn 't grabby, and it does n't get mushy when hot. But when we

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