REVOLUTIONARY NEW FOUR-STROKE
Yamaha's
revolutionary YZ400F four-stroke is a dynamic new motocross bike
that will open up a world of excitement in the off-road
community. Past statements concerning motocross four- strokes
were considered oxymoron's, however, the YZ400F is poised to
dismantle those beliefs. The YZ400F meets the market desires for
a motocross bred production four-stroke and joins the YZ family
as a purpose built, closed-course competition motocross bike.
Yamaha engineers initially began to build the YZ400F with a goal
to exceed all current production four-strokes. As ideas and
technology flourished, Yamaha continued to push the envelope to
surpass industry and customer expectations. The engineering used
on the YZ400F project produced a production four-stroke that not
only is capable of beating current four strokes, but rather, a
machine capable of running head to head on a motocross track with
production two-stroke 250cc motocross bikes.
Today's motocross tracks require quick, abrupt power and place
rigorous demands on suspension components. Challenges with
traditional four-strokes include poor handling on motocross
tracks due to 
weight, frame, and power delivery design. Until the
YZ400F, instantaneous acceleration from the motor was the key
ingredient four-strokes could not achieve. The liquid cooled
397cc 5-valve motor features a quick power snap with the turn of
the throttle, allowing a racer to jump obstacles on the track
that its two-stroke counterparts are attempting. Additionally,
the tractable four-stroke motor creates less wheel spin and
enables the rider to accelerate quicker on dry surfaces.
Because of its design goals, several components on the YZ400F are
similar to the Yamaha's YZ125 and YZ250. Front and rear disc
brakes, Kayaba front and rear suspension, frame geometry and
ergonomics parallel the state of the art two-stokes currently in
Yamaha's line-up.
The YZ400F will feature a single shaft balancer, 39mm Kehin
flat-slide carburetor, throttle position sensor, dry sump
lubrication, and a kick starter with a manual decompressor. The
target dry weight is 233 pounds.
The YZ400F will be available in Team Yamaha Blue/White and will
arrive in dealerships nationwide by December/January 1997.
Manufacturer's suggested retail price is $5,799.
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Just Released!
YAMAHA INTRODUCES 1998 WR400F
CYPRESS, Calif., (October 13, 1997) -- Yamaha Motor
Corporation, USA introduces its new off-road motorcycle, the
WR400F. The latest offering for the off-road community is an
offspring of the ground braking YZ400F. The WR400F relies on the
compact motor and chassis engineers attained with the YZ400F in
addition to accessories necessary for off-road riders.
The WR400F features the same 399cc five valve, liquid-cooled twin
cam engine, narrow chassis, Kayaba suspension, and brake system
as found on the YZ400F. Based on four- stroke technology achieved
with the YZ400F, Yamaha incorporated additional features designed
for the rider that chooses the open space over the tight tracks.
For greater versatility in the desert, mountains, or woods the
WR400F features an increased capacity CDI unit, a 60 watt halogen
headlight, a taillight, voltage regulator, tripmeter, 18"
rear wheel, 3.2 gallon fuel tank, wide ratio transmission, and
spark arrestor as standard equipment in 1998.
The WR400F is scheduled for release to dealers nationwide by
March, 1998 at a suggested retail price of $5,899.
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YZ250
Yamaha engineers set out to build upon the 1997 YZ250 by
improving the power delivery, suspension and ergonomics for the
1998 YZ250. We are happy to report, Yamaha test riders determined
the goals were achieved and the 1998 YZ250 will again heat up the
competition on the tracks next year.
Developments to the port timing and cylinder head design, coupled
with a new expansion chamber resulted in a harder hitting
midrange 
motor while increasing top end power. Increased
speed and power needed to be matched with improvements to the
suspension. New "works style" 46mm KYB forks feature
elastomer bottoming stoppers to overcome the harsh hit felt when
a rider jumps or lands hard off certain jumps. Rear suspension
changes, including a repositioned relay arm and connecting rod
allow for an improved cushioning effect on chopped out sections
or rough landings.
The rear disc was increased from 220mm to 240mm and the front
brake cable features an improved routing system, allowing the
rider to brake much later going into a turn. Even the seat was
carefully reshaped to allow the rider to more easily lay the bike
from side to side around berms.
Other changes for 1998 include repositioned handlebars for a more
aggressive riding position, a steeper front end geometry to
improve the bikes quick turning ability, and a new primary drive
gear for enhanced throttle response out of turns.
The YZ250 will be available in the popular Team Yamaha Blue/White
and will arrive in dealerships nationwide by September 1997. The
manufacture's suggested retail price remains at $5,599.
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YZ125
Yamaha's YZ 125 has proven to be the benchmark for production
125s in the industry. In 1996, the YZ125 was named the "Bike
of the Year" by one leading motocross magazine. To up the
ante, the 1997 YZ125 captured no less than five leading
motorcycle publication "Shoot-out" victories. Its
accolades in print parallel its impressive racing performances.
Described by many as a wonderful motorcycle, Yamaha engineers
never had time to bask in the glory as they felt improvements
could be made to the 1998 YZ125.
Yamaha made a number of enhancements to the 1998 YZ125, serving
notice that Yamaha plans to stay ahead for another year.
Suspension, brake, and motor upgrades will assure strong
performances in the highly competitive 125cc class.
To
match today's rigorous track obstacles and increased speeds,
Yamaha made key changes to the front fork internals.
"Works-style" Kayaba forks feature a unique bottoming
cone, longer stroke, and specially designed shims that enable the
suspension to work in harmony over the worst conditions.
Braking plays a major role throughout the course of a race.
Tapping the rear brake in the air to bring the front tire down,
applying the front brake delicately to stay in a difficult rut,
and sliding with the brakes to set up for a turn are required
uses for modem motocross brakes. Precise feedback and ample
strength are assets not to be comprised. For 1998, Yamaha's YZ125
and YZ250 feature new front and rear brake calipers, larger rear
discs, and rerouted Kevlar brake lines to assure quality 
performance.
Yamaha's engineers searched for a way to increase throttle
response. A lighter piston and piston pin generate quicker
response and increased performance in the high rpm range,
especially important in the wide-open 125 class.
The 1998 YZ125 will be available in Team Yamaha Blue/White in
dealerships nationwide by August 1997. Manufacturer's suggested
retail price remains at $4,799.
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YZ80
The 1998 YZ80 continues for 98. Featuring technology and
styling from its bigger brothers in the YZ line, the YZ80
features the required performance tools needed to add to the
bedroom trophy case.
The YZ80 dominated local events as well as the World Mini Grand
Prix. Driven to perfection in the highly competitive 80cc class,
the YZ80 has been the star pupil for the past three years. Yamaha
will again record high marks as refinements to the chassis and
braking system increase its performance.
Subtle improvements to the frame make it stronger and stiffer,
enhancing the overall handling. Building upon its purebred YZ
chassis, the frame design instills rider confidence while railing
berms or attacking technical sections of the track. To control
the bikes power and speed, the brake pad material has been
changed, allowing a more precise "one-finger" feel.
The YZ80 will be available in Team Yamaha Blue/White in
dealerships nationwide by September 1997. Manufacturer's
suggested retail price remains at $3,149.
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Specifications
1998 Yamaha
YZ400F
ENGINE
Type Liquid-cooled, 4-stroke, single cylinder
Displacement 399cc
Bore & Stroke 92 x 60.1 mm
Compression Ratio 12.5:1
Fuel System 39mm Keihin FCR carb. w/accelerator
pump
Valvetrain 5 valve-head w/dual chain-driven cams
Ignition Electronic CDI with throttle position
sensor
Starting Kick-start with decompression lever
Exhaust System Single header with aluminum
silencer
Drivetrain Clutch Dry sump lubrication
Transmission Constant mesh, 5-speed
Primary reduction 2 spur gear, 3.0:1
Secondary reduction Chain drive
CHASSIS/SUSPENSION
Chassis type Oil-carrying, semi-double cradle
frame
Overall length 85.3"
Overall width 32.2"
Overall height 50.6"
Seat height 38.5"
Wheelbase 58.3"
Ground clearance 14.7"
Dry weight 233 lbs.
Front suspension 46mm telescopic fork,
11.8" of travel
Rear suspension Swinging arm, New Monocross,
12.4" of travel
Shock absorber, front coil spring, oil damper
Shock absorber, rear coil spring, oil damper
STEERING/BRAKING
Steering type Taper roller bearing
Front brake Power assisted, Nissin drilled disc
(245mm)
Rear brake Power assisted, Nissin drilled disc
(220mm)
WHEELS/TIRES
Front wheel/tire Cast aluminum 21x1.6 /
80/100-21
Rear wheel/tire Cast aluminum 19x2.15 /
110/90-19
1998 YZ250
ENGINE
Type Liquid-cooled, 2-stroke, torque induction,
single
Displacement 249cc
Horsepower 50.5 bhp @ 8,500 RPM
Torque 33.93 ft-lb @ 7,500 RPM
Bore & Stroke 68mm x 68.8mm (2.68" x
2.71")
Compression Ratio 10.6:1
Fuel System Normally aspirated by one Keihin
PWM38/1
Ignition system CDI, kick start, 12V/7AH battery
(TBD)
DRIVETRAIN
Clutch Wet, multiple disc
Transmission Constant mesh 5-speed
Primary reduction Spur gear
Secondary reduction Chain drive
CHASSIS/SUSPENSION
Chassis Type Semi double cradle, 27.2 deg.
caster angle
Overall length 85.8" 2179mm
Overall width 32.6" 827mm
Overall height 51.3" 1303mm
Seat height 38.9" 989mm
Wheelbase 58.3" 1482mm
Ground clearance 15.4" 392mm
Dry weight 218 lb / 99 kg
Front suspension Telescopic fork, 11.81"
travel (300mm)
Rear suspension Swingarm link suspension,
12.4" travel (315mm)
Shock absorber, front coil spring, oil damper
Shock absorber, rear coil spring, gas-oil damper
STEERING/BRAKING
Steering type Ball bearing
Lock to lock angle 43 degrees left, 43 degrees right
Front brake Single disc brake (245mm)
Rear brake Single disc brake (240mm)
WHEELS/TIRES
Front wheel/tire Cast aluminum, 1.60 x 21
Rear wheel/tire Cast aluminum, 2.15 x 19
1998 YZ125
ENGINE
Type Liquid-cooled, 2-stroke, reed valve, single
Displacement 124cc
Horsepower 37.3 bhp @ 11,500 RPM
Torque 18.14 ft-lb @ 10,500 RPM
Bore & Stroke 47mm x 47.8mm (1.85" x
1.88")
Compression Ratio 8.9:1
Fuel System Normally aspirated by one Mikuni
TMX36SS/1
Ignition system CDI, kick start, 12V/7AH battery
(TBD)
DRIVETRAIN
Clutch Wet, multiple disc
Transmission Constant mesh 6-speed
Primary reduction ·Spur gear
Secondary reduction Chain drive
CHASSIS/SUSPENSION
Chassis type Semi double cradle, 25.6 deg.
caster angle
Overall length 84.2" 2139mm
Overall width 32.6" 824mm
Overall height 51.7" 1314mm
Seat height 39.1" 993mm
Wheelbase 56.9" 1444mm
Ground clearance 15.7" 400mm
Dry weight 196lb 71kg
Front suspension Telescopic fork, 11.81"
travel (300mm)
Rear suspension Swingarm link suspension,
12.4" travel (315mm)
Shock absorber, front coil spring, oil damper
Shock absorber, rear coil spring, gas-oil damper
STEERING/BRAKING
Steering type Ball bearing
Lock to lock angle 43 degrees left, 43 degrees
right
Front brake Single disc brake (245mm)
Rear brake Single disc brake (240mm)
WHEELS/TIRES
Front wheel/tire Cast aluminum, 1.60 x 21
Rear wheel/tire Cast aluminum, 1.81 x 19
1998 YZ80
ENGINE
Type Liquid-cooled, 2-stroke, reed valve, single
Displacement 83cc
Horsepower 27.6 bhp @ 12,000 RPM
Torque 12.32 ft-lb @11,000 RPM
Bore & Stroke 47mm x 47.8mm (1.85" x
1.88")
Compression Ratio 8.2:1
Fuel System Normally aspirated by one Mikuni
VM26SS/1
Ignition system CDI, kick start, 12V/7AH battery
(TBD)
Drivetrain
Clutch Wet, multiple disc
Transmission Constant mesh 6-speed
Primary reduction Spur gear
Secondary reduction Chain drive
CHASSIS/SUSPENSION
Chassis type Semi double cradle, 26.2 deg.
caster angle
Overall length 71" 1803mm
Overall width 28.9" 735mm
Overall height 43.5" 1105mm
Seat height 33.6" 854mm
Wheelbase 49.5" 1257mm
Ground clearance 13.7" 347mm
Dry weight 146" 71kg
Front suspension Telescopic fork, 10.83"
travel (275mm)
Rear suspension Swingarm link suspension,
11.1" travel (282mm)
Shock absorber, front coil spring, oil damper
Shock absorber, rear coil spring, gas-oil damper
STEERING/BRAKING
Steering type Ball bearing
Lock to lock angle 45 degrees left, 45 degrees
right
Front brake Single disc brake (220mm)
Rear brake Single disc brake (190mm)
WHEELS/TIRES
Front wheel/tire Cast aluminum 1.40 x 17
Rear wheel/tire Cast aluminum 1.60 x 14
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