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1971 Yamaha HT1 90 Enduro Motorcycle Road Test - 3-Page Vintage Article
Original, Vintage Magazine article.Page Size: Approx. 8\" x 11\" (21 cm x 28 cm) each pageCondition: Good
Yamaha’s replacement for their discontin-ued 80cc and lOOcc Trail models is thenew HT1 90 Enduro. The new 90’s forerun-ners were built strictly for off-road use, withlittle thinking done on/or provision madefor pavement operation. More versatile thanits predecessors, the new Yamaha 90 is puttogether for the expanding street-trail mar-ket. Like its competitors in the street-trailcategory, the HT1 is a compromise machine.The one remaining question is: what kind ofa compromise and how good?The 90 Enduro drops perfectly into thegap between the Mini-Enduro and the 125ATI. In fact, the 90 is a three-quarters repli-ca of the 125 Enduro; styling and layout fol-low the trend-setting DTI. The steel gastank and Autolube oil tank are painted a40deep metallic purple, and the finish on thevarious components is smooth and clean. Nosplattered welds, and no orange-peelingpaint either. The black three-quarter lengthseat has a pleated vinyl covering to hold therider’s seat on the saddle. The slight extralength in the saddle provides enough roomfor a passenger, so long as it’s a child or a90cc-sized wife. While folding footrests forboth rider and passenger are standard, thesuspension just barely handles one full-sizedrider, much less two.The upswept exhaust system, which car-ries a built-in U.S. Forestry-approved sparkarrestor, is tucked away from the legs of rid-ers and passengers. The chrome metal guardstays cool enough to touch even though it isfastened directly to the muffler body. Theinner baffle is removable, it should becleaned every 1000 miles or so for maximumperformance. Leaving the baffle out entirelyfouls up the exhaust tuning and increases theoperating temperatures of the engine. Thisin turn causes two things: a drop in the 90’sperformance and an ear-busting racketwhich will color neighbors angry. Leave thebaffle in; go faster in peace.The lighting system on the Enduro 90now includes turn signals as standard equip-ment, as do all street-legal Yamahas for1971. In traffic, the flashers give the bikerider a better chance of being seen by myop-ic motorists. And the new Yamaha tail-light—which is huge—may fend off otherinattentive car drivers seeking cheap thrillsat your expense. Unable to make the six-voltlamps any brighter, Yamaha has at leastmade things bigger and easier to see. On thetrailways lights can be extra baggage; thanksto the flywheel ignition, all the lights can bestripped away if the rider wishes.The wheels are 18-inch items on bothends. The trials-pattern tires are a goodcombination for street and moderate dirtriding, but they won’t do the job in mud.Different tires and a larger front wheelwould help, and Yamaha does carry a 21-inch front wheel as an option. Yet rewheel-ing and reshodding the Enduro 90 would re-semble lacing an old lady into track shoes.She would have the traction, but not the legsand knees. The Enduro 90’s suspension justisn’t up to much more than a fast clip over acow pasture. The front forks are similar tothose on the 125 Enduro, but they don’twork as well. The chromed shafts on the 90are . 125-inch smaller than the ATI and flexwhen normal limits are exceeded. Thedamping can be increased to an acceptablelevel by changing to a heavier SAE weightoil. The rear shocks have five different set-tings, ranging from bad to worse Even whenthe shocks are at the stiffest position a 150-pound rider can still bottom the unit. Thedamping is non-existent. When pumping theback end up and down, the only resistance isin the springs. Yamaha could have eliminat-ed the marginal suspension on the HT1 bymounting the forks and shocks from the 125ATI. The cost couldn’t have been that muchgreater, and the pieces will fit right onto thesmaller machine. Of course, these changeswould create a machine that is nearly equalto the 125cc ATI costing $100 more—some-thing Yamaha might not want to do.The machine’s mild steel tubular framehas a 1.25-inch backbone tube connectingthe steering head to the swingarm pivotarea. Smaller (,75-inch) double downtubescradle the engine unit. The rear subframe iswelded to a box-like affair that forms theswingarm connection point and ties into themain backbone right at the rear of the gastank. The entire assembly is quite rigid andseems strong enough to handle an enginewith twice the 90’s punch. The tubular swing-arm is gusseted on the forward end and easi-ly handles the weight and torque output ofthe HTl.The engine-transmission unit is the samephysical size as its bigger brothers, the 125and 175 Enduros. Many of the parts are in-terchangable, such as gears, clutch and kick-start pieces, oil pump, and the outer cases.Due to the 90’s shorter stroke, though, thecrankshaft assemblies can’t be swapped. Butthey both share the same size bearings. Witha lower-end capable of supporting twice itsdisplacement, the HTl internals should beas durable as rocks.In the past, Yamaha has used a rotaryvalve induction system for the lOOcc-and-under engines. The new 90 breaks traditionby using piston controlled ports with Ya-maha’s five-port transfer system for betterperformance. The cylinder on the HTl iscast iron with generous finning for a ma-chine the size of a 90, so the small singleshouldn\'t overcook and seize. The rod issupported by caged rollers at the big endand the wristpin rides in needles. The alumi-num cylinder head has a squish band com-bustion chamber like the larger Enduros,and the head features an extra tapped holefor a sparkplug or compression release.GYT-kit power can be bolted straight onto the HTl for $118. This includes a “port-ed” cylinder, high compression head, racingpiston with rings, 22mm Mikuni carb, ex-pansion chamber exhaust, and all the neces-sary brackets and gaskets to install it.Thanks to the extra strength of the lowerend, clutch and gear train, a GYT-kitted en-gine shouldn’t be strained. Yamaha claimsthat the additional power and low weight ofa kitted HTl give it the performance of a125, and this claim certainly seems reason-able..The 90 Enduro’s small size makes it anideal machine for the wife or small-to-medi-um adolescents. The low seat height andlight weight gives the smaller riders confi-dence. This enables them to learn to ridequicker and enjoy what they are doing. Thecontrols push, pull, and twist easily. The ig-nition key/light switch is mounted on thetop fork yoke and the turn signal and thehigh/low beam toggles live under the leftthumb. All are easy to reach and operate.The waffle-pattern hand grips cushion thevibrations and jolts of riding and allow a bet-ter grasp on the bars during wet weather.The footpeg rubbers are grooved to helpkeep feet from slipping off, and the engineshifts go through in short, crisp moves. Thiswide powerband and the five-speed trans-mission allow the rider to use his machinefor everyday around-town riding and stillramble down cowpaths on weekends with-out changing the overall gear. The rearwheel hub has a built in rubber shock absor-ber to take out road lurch before it poundsA crisis-sized taillight dominates the rear.The piston-port engine is a good 90cc slogger.Hard riding in the rough overtaxes the forks...16486
