1974-Yamaha-MX-and-Y..

1974-Yamaha-MX-and-Y..
 Nu
Standard 125 MX version shares
many of the same components.
There's only one logical question
and you know we're going to ask it:
“Is the 125 YZ worth the extra
money?”
And of course, there are only two
logical answers: “Yes and No.”
Huh?
Back up for a minute and take a
look at the differences in the two
bikes. You pay about $110 more for
a YZ than you do for an MX. The
trick stuff they give you is easily
worth that. No way could you buy it
that cheap if you paid retail for it on
the open market. Differences, basi-
cally, are as follows:
125 MX
Paint — yellow and black
Weight
16 horsepower
Mild steel frame
Oil injection
Steel rims
Normal ratio gearbox
Ordinary gas tank
Magneto ignition
Little bits and pieces made out of
ordinary metal
YAMAHA
125 YZ
Mostly silver gray
OP Less weight
@ 18.2 horsepower
Alloy steel frame (lighter)
Pre-mix
Aluminum alloy rims
; : E Close ratio gearbox
| It’s a confusing choice until High-zoot gas tank that weighs ex-
actly the same, but holds less
you find the facts— CDI ignition
Little bits and pieces made out of
then you just don’t care anymore ria sud meses
By the Staff of DIRT BIKE
| 62 DIRT BIKE
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1
Let us add it up for you. Lessee
. . . 35 bucks for the porting,
maybe 50 for the frame difference,
30 for the rims, 60 bucks for the
CDI and toss in 20 bucks for the
odd bits and pieces. Disregard the
visual stuff, as it does not make you
go any faster. Anyway, you get the
idea. Justabout 200 dollars worth of
goodies — some of which you may
not need or want — but still, a bar-
gain price for them.
What Yamaha has done, in es-
sence, is eliminate the middleman.
These things they have tacked on
the YZ are pretty much after-
market items that Yammie riders
have been bolting on their bikes for
years. If they could afford it, that is.
So in that respect, the YZ is most
assuredly worth the tab. But we
feel, in the final look, that overall
performance is not that much dif-
ferent from the plain old MX ver-
sion. Yes, the YZ is faster, but not
that much faster. Lap times for
most riders were about the same.
And on a tight, twisty course, the
standard model is actually a better
machine, except in the hands of a
top 125 class rider. Quite frankly,
that top 125 class rider will not be
on a Yamaha at all. There are better
bikes in this class. Faster bikes.
Bikes that handle in a superior
manner. Bikes that cost more.
Which is one of the big reasons
why so many riders are on the
1974 YAMAHA 125 MX
PRICE: $708, suggested retail
ENGINE TYPE: Reed valve, two-
stroke, single
DISPLACEMENT: 123cc
BORE & STROKE: 56mm x 50mm
COMPRESSION RATIO: N/A
CARBURETION: 28mm SC Mikuni
HP @ RPM: (claimed) None
(actual) 16.0 @ 8500 rpm
PRIMARY DRIVE TYPE:
Helical gears
PRIMARY RATIO: 3.894:1
FINAL RATIO: 3.13:1
CHAIN SIZE: #428
GEAR RATIOS: 1. 2.833
2. 1.875
3. 1.368
4. 1.091
5. 0.956
AIR FILTER: Wet foam
ELECTRICAL SYSTEM: Magneto
LUBRICATION: Autolube
FUEL CAPACITY: 1.8 gallons
RECOMMENDED FUEL: Premium
RECOMMENDED OIL: Yamalube
FRAME TYPE AND MATERIAL:
Mild steel
FORKS: Yamaha; 5.7-inch travel
SHOCKS: Thermal-flow;
4.2-inch travel
‘TIRES: Yokohama Front: 2.75x21
Rear: 3.50x18
RIMS: Steel
DIMENSIONS:
Wheelbase: 53.0 inches
Ground clearance: 10 inches
Seat height: 31% inches
WEIGHT: 195 with % tankof gas
and full oil injection unit
on front wheel: 85 pounds
on rear wheel: 110 pounds
FOOTPEG HEIGHT: 11% inches
HANDLEBAR HEIGHT: 40 inches
INSTRUMENTS: None
SILENCER: Yes; good
effectiveness
PRIMARY KICK: Yes
1974 YAMAHA 125 YZ
PRICE: $819, suggested retail
ENGINE TYPE: Reed-valve, two-
stroke, single
DISPLACEMENT: 123cc
BORE 8: STROKE: 56mm x 50mm
COMPRESSION RATIO: 8.0:1
CARBURETION: 28mm SC Mikuni
HP @ RPM:
(claimed) 23 @ 10,000 rpm
(actual) 18.2 @ 10,500 rpm
PRIMARY DRIVE TYPE:
Helical gears
PRIMARY RATIO: 3.894:1
FINAL RATIO: 3.357:1
CHAIN SIZE: #428
GEAR RATIOS: 1. 2.833
2. 2.066
=. MO)
4. 1.315
5. 1.142
AIR FILTER: Wet foam
ELECTRICAL SYSTEM: CDI
LUBRICATION: Pre-mix, 16:1 ratio
FUEL CAPACITY: 1.45 gallons
RECOMMENDED FUEL: Premium
RECOMMENDED OIL: Castrol “R”
30
FRAME TYPE AND MATERIAL:
Thin wall alloy steel
FORKS: Yamaha; 5.7-inch travel
SHOCKS: Thermal-flow;
4.2-inch travel
TIRES: Yokohama Front: 2.75x21
Rear: 3.50x18
RIMS: Takasago aluminum alloy
DIMENSIONS:
Wheelbase: 53.0 inches
Ground clearance: 10 inches
Seat height: 312 inches
WEIGHT: 189 with 1/3 tank of gas
Pra a... 81%2 pounds
Rear: rei bri he 107% pounds
FOOTPEG HEIGHT: 11% inches
HANDLEBAR HEIGHT: 40 inches
INSTRUMENTS: None
SILENCER: None
PRIMARY KICK: Yes
64
Yamaha line of budget racers in the
first place. Most of those faster, bet-
ter handling bikes cost well over a
thousand bucks — and need addi-
tional money to make them “right.”
Additionally, reliability on a stress-
ed European 125 MXer is not all
that wonderful. Just take a look at
the activity in the pits between 125
Expert motos. Parts are constantly
being worked on or replaced.
The Yamaha motocrossers, then,
are primarily sold to huge numbers
of Novices and play racers. They're
affordable machines, and do in-
deed seem to hold up well. None of
the budget buyers are content to
leave the bike alone — everyone is
constantly diddling with the carb
у | +
MXer is polished with some black.
and hanging on one miracle expan-
sion chamber after another — try-
ing to make the damn thing run like
a 400. Mostly, they just succeed in
altering the power curve and short-
ening the life span. Such is life in
the 125 class.
And life in the 125 class, in most
of this country, is crawling with jill-
ions of Yamahas. With this some-
what sobering thought in mind,
let's take a very long, very hard look
at the choice Yamaha is offering.
Obviously, the YZ has more
beans than the MX. At least on top.
But from 4000 rpm to 8500 rpm, the
standard motocrosser offers almost
a full horsepower more. Right at
8700 rpm, the YZ takes a deep
breath and goes nutty. Take a close
DIRT BIKE
peek at the dyno chart and you'll
see how steep the power curve is.
If riders of equal skill are placed
on the two different machines, the
winner will be largely dependent
on what level of skill we are exam-
ining. If both riders are below av-
erage in riding skill, the rider on
the standard model will probably
turn quicker lap times, especially it
the course is demanding.
The 125 MX is much easier to
ride, with the powerband being
tractable enough to allow trail rid-
ing. Second gear was strong
enough for even the tightest turns
on our test courses. As long as the
bike had any forward motion at all,
no clutch slipping was needed.
Typically well-mannered Mikuni carb
allowed both race bikes to start
easily and even idle.
2
3 2 4 ТА 4 *a
YZ front brake was magnesium —
MXer was the lower priced spread.
Some care had to be taken when
riding the YZ — selection of the
correct gear for the situation was an
absolute must. Unlike the MX, the
YZ didn't like to be forced at low
revs and would blubber and moan
if the motor was asked to work. A
moment too late at the shift lever
often meant that the rider had to go
down several gears to regain
momentum. There simply isn't
room for error in the YZ's engine.
In the hands of fairly skilled rid-
ers, the YZ would surely pull the
standard model — atleast down the
straights. Horsepower is, after all,
horsepower.
Togetanidea of the difference in
output, we drag raced both the
bikes a whole bunch of times,
JANUARY 1974
switching riders back and forth for
comparison. Invariably, the MX
would pull the YZ out of the hole
and stay a length or two ahead until
the bikes reached fourth gear.
Then, the YZ would start to stretch
its legs and edge ahead of the MX.
It's fairly safe to say that the YZ is
worth about one to one-and-a-half
lengths at the first turn. Top end on
both bikes is about the same, but
the YZ will get there sooner than
the MXer.
One interesting sidelight took
place while drag racing. A Honda
125 showed up on the starting line
with George Ethridge aboard. We
put Russ Darnell aboard the
Yamaha YZ and let him have a
string of passes to get used to the
bike. Then, George and Russ
punched off 11 straight passes —
the YZ winning all but one. Yup. In
a straight line drag race, the YZ will
edge ahead of a standard 125 CR
Honda. A standard Honda, by the
way, means one that is jetted too
rich. As of this writing, Honda has
not offered an assortment of jets for
their bikes, and all of them come
jetted far too rich. Shame. That
means that, as delivered, a stock
CR125 is down two, maybe three
ponies. The Honda will, however,
pull the MX version a bit. The big
difference happens on the track,
though, where the 125 Honda's
broad powerband (5000 to 8000
£28 5
Rear hubs look the same, except for paint. YZ assembly
is a bit lighter.
65
ah
— he wile” CN a 2
MX version had enough tractable
power to be trail ridden.
rpm) puts it on the YZ fairly well.
Still, we preferred the power
characteristics and output of the
standard MX Yamaha over both the
YZ and the Honda. It sure would be
nice to own a Honda with a Yamaha
MX engine.
HANDLING
All things considered, the MX
handled better than the YZ. Yes,
the YZ is lighter, but the narrow
powerband made the bike spooky
compared to the cheaper model.
Horsepower directly affects hand-
ling, and these two Yamahas prove
this point rather clearly. Both chas-
sis are identical in dimensions, but
the MX is much easier to ride
quickly. And on bikes with margin-
al suspension components, this is
forcefully brought to light.
Mounted on the rear of both rac-
ers are Yamaha's very own
Thermal-Flow shocks. While these
shocks work OK on the big
Yamahas, on these lighter bikes
they appear to be a classic case of
overkill. Even some of our
beefeater-type testers complained
that the springs were too stiff.
When you consider the fact that
most 125 class riders are smaller in
stature, one can only wonder why
Yamaha didn’t cut that spring rate
right in half.
Adding to the suspension prob-
lems is a set of forks (on both
machines) that are positively loath-
some in their performance. Yes,
they move up and down — but
that’s about all they do. Harsh im-
pact is transmitted directly to the
rider — causing hands and arms to
tire prematurely from the beating.
JANUARY 1974
Both bikes share same bars,
And no, a change of oil will not cure
the problem. At least not any oil in
this world that we know of. These
forks are not only a step backwards,
but a giant leap into the past. They
appear to be the very same trash
that is mounted on the Enduro line.
Maybe they re not — but who re-
ally cares when they don't get the
job done.
seats, miscellaneous hardware.
Adding to the staggering mis-
eries in the handling department
are the tires. These wretched ex-
cuses for knobbies are sooooo bad,
that we can only guess as to what
the chassis really handles like.
Yokohama is the culprit and lack of
traction is the crime. No knobs to
speak of are on the sides and any
time the bike is leaned over, the
67
or se,
as
Skinny front tire on both bikes, combined with average
chassis, made for several of these numbers.
square profile of the tire creates a
panic situation. Even when the
bike isn’t moving. The shape and
pattern are much like that of a
15-year-old Dunlop and you know
how grim those things were.
Because of the square shape, if
the bike has to make an abrupt
change of direction on anything
less than an ideal surface, the
HORSEPOWER AT REAR WHEEL
4,000 5,000 6,000
machine will take little breath-
stopping hops outward. Or maybe a
big hop. And on hard packed dusty
surfaces, the rider will find himself
in a constant state of recovering
from a case of Terminal Wiggles.
Like we said, the frame might be
good, but we really don’t know be-
cause the rubber refuses to cooper-
ate with the rider.
7,000
RPM
8,000 9,000 10,000
с ade
Both bikes had well tucked in pipes,
but could have used some heat
shielding near the knee contact area.
In straight line handling, the
Yamahas both appear to handle bet-
ter than in years past. Some rear-
end hop is apparent, but not any
queasy tank-slapping stuff. Aside
from motocrossing the hell out of
both bikes, we also took them out in
the desert and entered a 50-mile
hare scrambles. Here, both bikes
worked well, but the MX version
a
Stinger broke off 125 MX ES didn't
seem to hurt performance.
-
a 3 + sg
Me A
Wretched knobbies allowed bear ehe
to wiggle out under power-like this.
DIRT BIKE
Big deal drag race — MXer would pull YZ through lower
gears — but not down any long straight.
was clearly a better cross-country
machine. Especially when climb-
ing a loose hill, or attempting to
shift up in deep sand. On the YZ, if
the upshift was less than perfect,
some clutch slipping or a downshift
was in order. Too, the gearbox on
the MX version proved more flexi-
ble under more conditions.
Under racing conditions, we
Deep sand made small engine work — bu
JANUARY 1974
- -
were able to get only 30 miles out of
the MX gas tank and about 25 from
the smaller YZ tank. Definitely not
even enough for a long moto. Of
course, a trail rider or desert racer
will want to fit a larger tank to the
bike, but any motocross bike
should carry enough fuel for a
45-minute moto.
t didn’
throttle
t hurt it.
Andy |
Banes
just for fun.
IN GENERAL
Braking has always been a
Yamaha strong point — perhaps too
strong on the rear, but both of these
little racers are far too prone to rear
wheel lock-up and subsequent en-
gine stalling. Even after we bent
the brake rod for sponginess (a cure
we ve used on many bigger Yam-
mies), we were still stalling the en-
gine often. Front brakes, on both
bikes, are superb as per usual
Yamaha practice. Water didn't
seem to have much effect on either
end of the bike's braking system.
One or two seconds with the brakes
applied got them back to original
strength.
Shifting was beyond reproach on
both racers — neutrals were caused
by rider error, not by the gearbox.
Even with the much shifted YZ, it
was clickitty-click, with or without
the clutch.
When first riding either bike, test
riders complained of poor layout
and feel. Nothing seemed to be set
up for rider comfort. Knees are
drawn up too high when sitting and
the bars induce a strange crouch.
The bike appears to have been de-
signed for a four-foot, ten-inch rider
with his crotch located an inch
above the collarbone. Both bikes
DIRT BIKE
feel shorter than they actually are,
but the tape shows 53 inches on the
wheelbase, with another inch and a
half left in the chain adjusters.
The more the bikes were ridden
(like most bikes), the more com-
fortable they felt. Still, they are not
relaxing machines to move around
on. One always has the feeling of
being on the end of a tall chair.
Whatever.
BITS AND PIECES
Chains on the YZ and the MX are
identical. Pathetic. They kinked
and stretched, rekinked, re-
stretched and retightened. We
lubed and adjusted until we were
sick of the damn things. Right be-
fore one moto, we oiled the chain
JANUARY 1974
up for a half-hour and left it a little
on the loose side. At the end of the
moto, it was as tight as a drum. This
was on the MXer and we had simi-
lar happenings on the YZ. This
chain should be taken off before
the bike is ever ridden, and used to
tie down a foo-foo dog somewhere.
If you don’t mind the critter es-
caping, that is.
Servicing the air filter is a minor
hassle. Seems the filter doesn’t
want to squeeze out between the
frame rails, so you have to deform it
a bit. While you're deforming it,
crud from the dirty filter drops right
down into the air hose and you’ll
have to take that apart, too. The fil-
ter is one of those fuzzy foam things,
that sheds hair like a sheep dog.
Twin-Air, Filtron, Uni and K&N all
offer replacements. Buy one.
Fenders are first-rate on both
bikes and lived through several
crashes. Good stuff.
Rims on the YZ are aluminum
alloy with mud-catching ridges,
while the MXer uses steel rims that
don’t catch mud, but bend easily.
Six of one . . .
Both bikes have a horrible case of
rear-end chatter when braking
hard. Neither sports full floaters.
Both need it.
Saddle is decent on the bikes and
holds up well. Like most, it’s slip-
pery when wet.
Neat clamps and rubber boots
abound on the bikes. Everything is
held in place snugly.
Our exhaust broke off the MX
(just the tip of the stinger) and
didn’t seem to hurt the power or
make the bike any louder.
The YZ was so loud that we hated
to ride it anywhere. For the racing,
we installed a J&R silencer we had
lying around. It didn’t seem to hurt
the power any. Might have even
helped ita bit down low. Of course,
that’s just a seat-of-the-pants guess.
Nothing leaked on either bike
during the entire test. Good.
Footpegs were nifty items and
held the boot well.
Overall finish on both units was
very good and both bikes are very
good looking, if that means any-
thing to you.
SUMMATION
Quite frankly, we like the yellow
standard MXer much better than
the YZ. It is a far more versatile
motorcycle and much easier toride.
Because of the smoother power de-
livery, handling seems superior to
the YZ and at racing speeds, the
MX is less tiring.
We wish Yamaha had taken the
extra $110 and spent it on suspen-
sion, though, instead of hot rodding
the motor.
Face it, both of these bikes will
be purchased mostly by Novices
and play racers and they need bet-
ter handling, not more horsepower.
To answer that question we
posed earlier, yes, the YZ is worth
the difference in money. But they
could and should have spent the
money differently. We're positive
that a rider on a properly sus-
pended MX could beat hell out of a
rider on a stock YZ. And that’s what
racing is all about, isn’t it? о
71
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