Cycle News - Archive Issues - 1980's

Cycle News 1983 02 09

Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles

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cover that your knees have no problem tucking into th e gas tank, which is smaller this yea r by 1.3 liters. If yo u' re worried a bo u t being able to go 40 minutes, don 't be - the Power Valve system helps save fuel. . Once the throttle was nailed. th e rear IRC 130/80-18 tire had no problem getting traction and lift ing th e front wh eel. Speak ing o f wheels, they're laced to aluminum ri ms that feature " ho llow" flanges o n th e sides to reduce u ns p ru ng weight. On th e track th e beauty o f the little yellow screa me r started to shi ne . In th e whoops, the 12 inc hes o f trav el u p fro n t was as pi ush as th e finest mattress. T he rea r sus pe nsion, on th e o ther hand , was set up for so meone much hea vier th an o ur band of test pil ot s. O nce adjus ted and with so me of th e preload tak en o u t, th e a lmost 12.5 in ch es o f tra vel handled an vthi ng it enco untered with no problem. Using the brakes was a no ther story. They work - almost too well. We locked them up mor e than o nce while we were ge tting used to them , bu t once we mas tered it the Ya ma ha allowed us to go much deeper into corners before we hit the binders. Speak in g of corners, th e Yam a ha ac ted as though it were on a monorail system beca use the fro nt en d stuck so well. Coming o u t of th e corners wa s done with gusto. Fann ing the easyto-use a nd fade-free clutch keeps the engine running in hyper-space realm. Peak pow comes on a little later in the rev range than last year, but it keeps going a little longer. In th e interest of reliability, las t year 's O-ring head gasket has been changed to the regular variety for better sealing. The 1982 model had trouble with the dura bili ty of the Power Valve, wi th the lin kage developi n g excessive pl ay after as litt le as 10 hours of ridi ng . Yamaha took care of that this year by adding a co llar between the pins and the joints to get a bigger bearing surface. This not o nly gives it additional durabil ity . but gives th e Power Valve a smoo ther throw action. A little tri ck Scheidler recommends: " T a ke a little Dr y Slide a nd hit each o ne of those joints. This not on ly extends the life of them , but allows the Power Val ve to ope n all the wa y all tfie ti me." · . Jumpingwas som ething the Yamaha lik ed to do. Beca use of the light weight, on ly minimal body English was required. Shifting th e YZ was quick. positive and a lmost effort less. However , we d id los e th e spring retaining-pin o n th e folding sh ift lever. Findin g th e sh ift lever an d brak e pedal was never a problem si nce th ey're positioned just right. Even th e sma ll pegs had enough teeth in th em for good footing. The 125K did everything we asked o f it a nd mor e, but sinc e we got o urs di rectly from Yam aha it had already been thoroughl y p repped. Sche id ler had a few su ggestio ns for the ri der who bu ys h is o ff th e sho wroom floo r: "The first thing one shou ld check is the timing , just to mak e sure it's set righ t. T he n go th rough the entire carburetor to make su re everyth in g is clea ned o ut, a nd don ' t for get to check the floa t bo wl level. (Need less to say. Yama ha lube R wa s in o ur test bi ke, mixed 30: I. ) "Drain the oil , in the tra nny and replace it wit h Cas tro l 20-50 weight. Ma ke su re all the pivot points on the mo nos hock are lu bed, incl uding the zerk fitti ngs . Next. make sure you p u ll th e rear wh eel off and check the bac ki ng pl a te an d the whee l bearings, an d use a high tempera tu re grease, say Bel-Ray. This is a n area nobody thinks a bo u t. and they will seize. " Also , chec k th e ch ain block to make sure it 's a lig ned and not hitting one side or the other. You sho u ld also take th e two bolts that hold th e chain guide in pl ace and Loc tite those. Check the rebound, compression and pre-load setti ngs on the shock to see where the y're at and if they suit your weight and the type of track you're going to be raci ng on. "Take a look a t the Po wer Va lve to ma ke su re you 're getting maximum opening; sometimes th ere may be another half a millimeter yo u can squeeze out of it. It 's just a matter of paying attention to the litt le things - th ey'll get you in th e end if you neglect them. " After riding th e YZ125K and listening to Sch eidler yo u get the impression that Ya ma ha is very serio us about 1983. T he seri ousness shows in the 125K - it 's a serious racer. • S pacifications Engine Type Two-stroke. reed -va lve single . 123cc. D isp lacement Bore 8< stroke 56 x 50mm. Compress ion ratio 7 .8 :1 to 9 .9:1 . Maximum torque (claimed) . . . . . . . . • . . . . .. 15.1 ft.-Ibs. @ 10.500. Carburetor . . . . . . . . . . . . . . . .. . .. . . . . . . • . . . .. . . . . . . . Mikuni. VM34. Igni tion , Capacitor discharge. Starting _.. .. .. . . . . . . . . • . Primary kick. Lubrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Premix. Transmission . .. . . . . . . . . . . . . . . . . . . • . . . . . . . . .. ..... . . . . Six-speed. Chassis . Overall length 84.1 in. 33.6 in . Overall width Overall height ... .. ...... . .. . . . . . . . . . .. . .. .. . • . • . . . . •. .. . 48.8 in. Seat height 37.0 in . 67.1 in. Wheel base Ground clearance ... • . . . . . . . ... .. . . . . . . . . . . . . ... , 13.8 in . Dry weight 190 Ibs . 1.8 gal. Fuel tank capacity Telescopic fork. Suspension front Rear Swingarm w ith monocross suspension. Drum. Brakes front Drum. Rear Tires front 3.00-21 . Rear 4 .10-18. Suggested retail price $1 .769 J ' , . • • I'-~--.....;..;--:;------..;..~ 11

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