rdcelestThe choice in the 125 c/ass gets one bike harder

Confidence is the key. There is noway that you can really ride amotocross quickly unless you haveabsolute confidence in your ownabilities and those of your machine.The true worth of a motocross biketo you is measured by what kind oftune it plays in the spaces of yourmind as you click it down throughthe gears and pitch it screaming intoa rutted, loamy turn. Whathappens, happens. How you feelabout what happens is maybe moreto the point.

Up until now, the 125cc YamahaMX series motorcycles have alwaysplayed a shaky tune. Twitching backends and bucking fronts kept riderconfidence levels lower thanbasement plumbing, while anemicfive-speed engines kept speeds lowenough to make falling off safe. fu aresult, the MXl2Ss were always

considered to be good trailbikes; butas racers the series iust didn't makeit.

This year, Yamaha has redesignedthe 125 MX, making it into a full-onracing machine that still comes stockwith a U.S. Forestry Serviceapproved spark arrestor. Now, the125 MX is not only a dynamite

"The bike seems likely tomaintain its reputation fordurability, while building anew one for competitiveness."

"There's something to be saidfor the dual-purpose conceptwhen it's executed correctly."

trailbike, but an excellentboot. There's something to

for the dual-purpose concept whenit's executed correctly.

Replacing last year's standard-mount Thermal Flow rear shocks arenew gas Kayabas with a single-ratespring, and mounted in the laydownposition. It's a setup similar to thatof the RM Suzukis. Yamaha insiststhat their gas Kayabas are betterthan Suzuki's gas Kayabas.Whatever. The relevant truth of thematter is that gas Kayabas, whetherthey're on a Suzuki or a Yamaha,wear out very quickly (like in fiveraces if you're gassing it), so itdoesn't matter much whose atebetter. We detected no significantdifferences in terms of shockfunction.

While the Kayabas work, theywork very well - as does the entiremechanical package whichcomprises the MXI25C. All thethings which made the old MXs nomore than just good trailbikes,things like oil injection, spookysuspension and a poky engine, aregone. In their place the MXC debutsa really powerful, six-speed YZ-likeengine that gets you the holeshotsand spits you out of turns like awatermelon seed, and a suspensionthat, while not perfect, can be dealtwith.

But the MXC is not simply aYZ ofa different color. The things thatmade the old MX a neat bike to own,things like dependability, durabilityand low maintenance costs, are stillthere. They've just been madebetter. For instance: The engine,though ported to YZ specs, still hasan iron cylinder liner that can berebored if you happen to waste apiston. The YZC's cylinder, whichhas a chrome bore, must berechromed or replaced if damaged.Ilave you ever tried to have acylinder rechromed? Most peopleend up having to buy a new one.

Then there's the suspension. It'snot a perfect package, but it can be

MOTOCROSS/MARCH 1976 47

racer tobe said

The Yamaha MX125G: an absolutelycompetitive bike that isunderctandable,

I{AMAHAMXI2SClived with, and it avoids some of thehassles of the monoshock system likeset-up difficulty, weight and air boxrestriction. The saving grace of theMXC's rear suspension is that it isunderstandable. Motocrossers havebeen dealing with shock absorbersand springs for a long time. We canget into a shock absorber and get itworking just right for our own

particular style. While themonoshock system is something that

"Allthe things which made theold MXs no more than justgood trailbikes . . are gone."most people (and a lot of dealers) areafraid to screw with, a moreconventional system like that of the

MXC can be personalized withoutundue trauma,

That's something the evenrelatively serious racer will have todo soon after buying an MXC.Suspension has never been a strongpoint on Yamahas, and the MXC isno exception. It starts off feelingpretty good, but soon the forks startbottoming and you begin to lose

Gas pressure Kayaba laydown shockswork well for a while. Spring rateswither with time.

Spokes, both f ront and rear assemblies,never came loose, a rarity among testbikes. Forks kept the wheel on theground up to a point. Pitching it atspeed over bumps would cause loss ofcontact and a wash.

Fork position is adjustable over atwo-inch span, cables are heavy-dutyand smooth working. Brake cable iswell guided and doesn't hang up on thefork tube.

Pipe disconnects easily at this point forquick access to the cylinder. The wholebike is the most easily serviced of anywe've tested.

48 MOTOCROSS/MARCH 1976

Air cleaner design, usually the weaklink on a Yamaha, is so boss on theMXl25C that it is actually fnbk

Weight saving is apparent on the MX.YZ-type bobtailframe and short fendermake up for the weight of themirffler/spark arrestor. The U.S.Forestry-approved u nit doesn'tintimidate power output at all.

your confidence in the shocks. Thesubstitution of l90cc of Bel-Ray30-weight in each fork tube settlesthe front end down a little, and acouple of clicks on the shock springadjusters sets the back up iust right.But after a few hot practice sessions,the forks start feeling squirrellyagain and the shocks fade. The frontwheel seems to want to dance on thebumps, giving you a dreary feeling

Six-speed YZ engine with an iron sleevedelivers some of the finest power we'veever experienced from a 125 stocker.Footpegs are very slippery on a wettrack. Kickstarter is a little awkwardand your knee will occasionally contactthe pipe.

". . . one of the mostserviced bikes we'vetested."

about what's going on below. Afront end that jitterbugs through acorner doesn't do much for your

bad. But as the springs begin toweaken - and they'll do that soonerthan you expect - the ride begins toget unmanageable. Yamaha needs toget their hydraulic pressures workedout more completely, and to getturned onto some good springs.Otherwise, as in the case of theMXC, the new owner's firstconsideration must be to upgradethe suspension. Continued

easilyever

confidence. When the shocks fade,they begin to return a little toosmartly for our tastes, but it's not too

MOTOCROSS/MARCH 1976 49

I.{AMAHAMXI2SCThis is not to say that you can't

wail on this bike in stock trim. Whilethe suspension isn't quite there, thepersevering rider is well-served bythe excellent frame, engine and tirepackage. While the chassis is madefrom the same light-duty steel thatconstitutes most Yamaha frames, it isconstructed in short enough sectionsto make the frame fairly rigid. Youmight say that it's a YZ framewithout the monoshock. Much of thevertical stress that caused last year'sMX swingarm to flex so much isrelieved by the laydown shockarrangement this year, so deflectioncaused by side loads is much lessapparent. And the added travel ofthe laydowns - 5.8 inches - helpsto make the rear end more stable.The result is a machine whichhandles better than you might atfirst suspect.

The power produced by theYZ-ported six-speed is excellent. Wealways felt that the reed valve l25ccYamaha engines lacked the top end

"The new MX125C is definitelya better machine, becauseafter it tickles your alarmcenters to see if you're awake,it gives you back the handle soyou can save it."

power necessary to compete withrace-tuned Hondas. The top endslump endemic to the Yamahas was,we felt, a function of the reed valveinduction system. But a few rides onsome factory-prepared Yamaha YZsconvinced us that the power wasthere, it just has to be coaxed outwith the proper port work and pipetuning.

That work has been done. TheMXC has all the power you'll need tobe competitive against almost any125. In stock trim, burning a hefty20:1 pre-mix and with the sparkarrestor still attached, the MXI2SCcomes on like a KXl25 Kawasaki,and keeps delivering all the way tothe top. We were very impressed.

For the novice, the reed valveinduction still gives the addedadvantage of clean running even atimpossibly low crank speeds. Youcan pull it from anywhere in anygear and never fog the spark plug.This gives the bike a decided

50 t\4oTocRoss/MARCH 1976

Heavy hits will keep the Yamahaskittering until the suspension settlesdown. which makes two nasty jumps ina row something to deal with.

Good tires keep the MX sticking longerand excellent throttle response gets theYammie away faster than mostproduction 125s.

advantage over many highly tunedcompetitors, especially when theaction hits sand or mud.

Staying onproblem withbut keeping tanother storypower output and the somewhatiadical porting, Yamaha stronglYrecommends in the owner's manualthat the piston and ring be replacedaJter eoery race. Whle this maYseem a little excessive, consideringthe pipe wrench durability of pastMXs, this is not an unreasonablerequirement. If you're not racing,

just riding, you should still pop for anew piston assembly every fewweeks. Take our word for it.

Keeping your confidence at theMarty Smith level when yoursuspension is doing a tap dancethrough the turns can be a chore ifyour tires aren't doing the iob. Thisyear, Yamaha has shod the MXmodel with a sano set of DunlopSports. Between the wraparound4.10 on the back and the sticky 3.00on the front, there's more thanenough prime rubber on the ground

Cont'd on page 67

SPECIFICATIONS

Make. .YamahaModel . MX125CCountryof Manufacture, . . . . .JapanRetailPrice . ... ..$890

ENGINEType:

Two-stroke, single-cylinder, reed valve

Bore I Stroke .56mm x 50mmDisplacement ..... ....123ccCompressionRatio . ....7.5:1Cylinder . Five-port, iron sleeveCarburetion: 30mm Mikuni (VM30SS )lgnition ....CDlLubrication .....Pre-mix2O:1Air Filter . . Fuzzed foam

TRANSMISSIONType . . . . .Six-speed, constantmeshRatios:

2.538, 1.933, 1.555, 1.300,1.142, ',t.045

Primary ...HelicalgearRatio. ....3.894Drive Chain . DK428HD

SUSPENSIONFront . . Sprung hydraulic forksRear:

Pressurized hydraulic shocksand springs, laydown position

Travel: 6.5 inches front, 5 inches rearDIMENSIONS

Wheelbase . .54 inchesGround Clearance . 10.8 inchesSeatHeight ......33.5inchesTrackWeight .... 189poundsWeight Bias:

44 percent front, 56 percent rearCAPACITIES

Fuel .. .....1.5gallonsTransmission..... .....650ccForks. . . 190.5cc

White on black with red trim and a setof businessman's tires makes the MXacceptably hairy looking.

\.

Ii

MOTOCROSS/MARCH 1976 51

YAMAHA MXI25C

Cont'd. from page 57

to get the job done. The MXC willskitter on a bumpy surf ace,especially when you're setting up fora turn, but each time the tires take abite they deliver enough of those"good traction vibes" to calm yourbrain and keep you on the gas.

The skipping suspension,combined with all that deluxepower, means that this bike has adefinite limit, one which anyreasonably skilled rider can reach.And that means that every once in awhile you'll be doing one of thoseradical fourth-gear rail shots alongthe outside of a sweeper (somethingthat's a great deal of fun on this bike)and the front wheel will suddenlytake a wash. This is when motocrossgets thrilling. You're sitting on thetank, backing it in, with your rightleg out as far as it will go, and yourfront wheel suddenly feels like it'srunning on linoleum. Your braintakes a 50-amp shot of pure terror.Your muscles tighten, you .

In the old days, this is when youwould kiss your "better machine"good-bye. But the new MXI25C isdefinitely a better machine, becauseafter it tickles your alarm centers tosee if you're awake, it gives you backthe handle so you can save it. Weused to call a bike like this"forgiving," but that was before wefound out that a really good bikedoesn't get you into trouble in thefirst place. Save the Iittle Yamahathis way a few times, and you startto develop a technique for breakingthe front wheel loose, even in thehairiest turns.

After you grow familiar with theadhesion limits of the front wheel,you begin to really jam it into thecorners hard. Ninety-nine times outof a hundred you'll come out smackon your line in a sweeping cross-up,roosting all over the opposition. Butevery once in a while the limit showsup, and the back end comes aroundas though you'd just run over a frog.

Which is to say that this is theperfect bike for the beginningmotocrosser. It's not so overly radicalas to scare a new rider, but it's not sotoady as to get boring after thenovice has mastered a few tricks. Itis also one of the most easily servicedbikes we've ever tested. The air boxis so effective and easy to service that

Contiruted

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MOTOCROSS/MARCH 1976 67

YAMAHA MXI2,C

Contirnted

it borders on being trick. The pipedisconnects forward of the silencer/spark arrestor assembly for easyaccess to the cylinder. Unlike eoeryother Japanese bike we've testedlately, the MXC had virtually nospoke problems. We tightened themonce after break-in, and never againhad to touch them. The wheelsrequired only occasional adjustment.

The engine, too, seems deadreliable. We like Yamaha'srecommendation of frequent pistonreplacement, because it teaches thenew racer the all-important basics ofgood engine maintenance on racemachinery. But just to see whatwould happen, we left the originalpiston assembly in for three testsessions and a race. Other thanthings sounding a little loose, therewas no damage. Still, we don'trecommend this procedure to theowner/racer.

As a matter of fact, during ourentire test of the MXC the onlyproblem which surfaced was a slightcrack in the gas tank seam - not

unusual on any machine. Thus, thebike seems likely to maintain itsreputation for durability, whilebuilding a new one for competitive-ness. Can't beat that.

There are a lot of new people whoare going to get interested inmotocross this summer. For them,the Yamaha MXf25C is the perfectchoice to go racing on during theirfirst season out. It's fast and reliable,and handles well enough to makethe novice h"ppy for a long time.And, if properly maintained, it willlast a long time. Our quibbles aboutsuspension can be easily mollifiedwith trick shocks at the rear, andsome individually satisfactorypackage of oil, springs or a fork kitup front. Some riders won't even feelthis is necessary and will leave theirMXCs stock. The stock bike willhandle anything you can put itthrough up until the time you feelyou've reached a skill level whichdemands a more sophisticatedmount. So if you're a new racerlooking to invest in a motocross bikefor the summer wars, at $890 (f.o.b.West Coast - $897 f.o.b. EastCoast), the Yamaha MX125C justcould be the best deal around. M