2004 YAMAHA YZ85 engine

1 - 15
GEN
INFO
STARTING AND BREAK-IN
CAUTION:

After the break-in or before each race,
you must check the entire machine for
loose fittings and fasteners as per
“TORQUE-CHECK POINTS”.
Tighten all such fasteners as required.

When any of the following parts have
been replaced, they must be broken in.
CYLINDER AND CRANKSHAFT:
About one hour of break-in operation is
necessary.
PISTON, RING AND GEARS:
These parts require about 30 minutes of
break-in operation at half-throttle or less.
Observe the condition of the engine care-
fully during operation.

GEN
INFO
1 - 16
TORQUE-CHECK POINTS
TORQUE-CHECK POINTS
Frame construction
Combined seat and fuel tank
Engine mounting
Steering Steering stem to
handlebar
Suspension Front Steering stem to front
fork
Rear For link type
Rear Installation of rear
shock absorber
Rear Installation of swin-
garm
Wheel Installation of wheel Front
Rear
Brake Front
Rear
Fuel systemFrame to rear frame
Fuel tank to frame
Frame to engine
Steering stem to upper bracket
Upper bracket to handlebar
Front fork to upper bracket
Front fork to lower bracket
Assembly of links
Link to frame
Link to rear shock absorber
Link to swingarm
Rear shock absorber to frame
Tightening of pivot shaft
Tightening of wheel axle
Tightening of wheel axle
Wheel to rear wheel sprocket
Brake caliper to front fork
Brake disc to wheel
Tightening of union bolt
Brake master cylinder to handlebar
Tightening of bleed screw
Brake caliper to bracket
Brake disc to wheel
Tightening of union bolt
Brake master cylinder to frame
Tightening of bleed screw
Fuel tank to fuel cock
NOTE:
Concerning the tightening torque, refer to
“MAINTENANCE SPECIFICATIONS” section
in the CHAPTER 2.

1 - 17
GEN
INFO
CLEANING AND STORAGE
EC1B0000
CLEANING AND STORAGE
EC1B1000
CLEANING
Frequent cleaning of your machine will
enhance its appearance, maintain good overall
performance, and extend the life of many com-
ponents.
1. Before washing the machine, block off the
end of the exhaust pipe to prevent water
from entering. A plastic bag secured with a
rubber band may be used for this purpose.
2. If the engine is excessively greasy, apply
some degreaser to it with a paint brush. Do
not apply degreaser to the chain, sprock-
ets, or wheel axles.
3. Rinse the dirt and degreaser off with a gar-
den hose; use only enough pressure to do
the job.
CAUTION:
Excessive hose pressure may cause water
seepage and contamination of wheel bear-
ings, front forks, brakes and transmission
seals. Many expensive repair bills have
resulted from improper high pressure
detergent applications such as those avail-
able in coin-operated car washers.
4. After the majority of the dirt has been
hosed off, wash all surfaces with warm
water and a mild detergent. Use an old
toothbrush to clean hard-to-reach places.
5. Rinse the machine off immediately with
clean water, and dry all surfaces with a soft
towel or cloth.
6. Immediately after washing, remove excess
water from the chain with a paper towel
and lubricate the chain to prevent rust.
7. Clean the seat with a vinyl upholstery
cleaner to keep the cover pliable and
glossy.
8. Automotive wax may be applied to all
painted or chromed surfaces. Avoid combi-
nation cleaner-waxes, as they may contain
abrasives.
9. After completing the above, start the
engine and allow it to idle for several min-
utes.

1 - 18
GEN
INFO
CLEANING AND STORAGE
EC1B2001
STORAGE
If your machine is to be stored for 60 days or
more, some preventive measures must be
taken to avoid deterioration. After cleaning the
machine thoroughly, prepare it for storage as
follows:
1. Drain the fuel tank, fuel lines, and the car-
buretor float bowl.
2. Remove the spark plug, pour a tablespoon
of SAE 10W-30 motor oil in the spark plug
hole, and reinstall the plug. With the engine
stop switch pushed in, kick the engine over
several times to coat the cylinder walls with
oil.
3. Remove the drive chain, clean it thoroughly
with solvent, and lubricate it. Reinstall the
chain or store it in a plastic bag tied to the
frame.
4. Lubricate all control cables.
5. Block the frame up to raise the wheels off
the ground.
6. Tie a plastic bag over the exhaust pipe out-
let to prevent moisture from entering.
7. If the machine is to be stored in a humid or
salt-air environment, coat all exposed
metal surfaces with a film of light oil. Do not
apply oil to rubber parts or the seat cover.
NOTE:
Make any necessary repairs before the
machine is stored.

SPEC
2 - 1
GENERAL SPECIFICATIONS
EC200000
SPECIFICATIONS
EC211000
GENERAL SPECIFICATIONS
Model name: YZ85 YZ85LW
YZ85S (USA)
YZ85LC (EUROPE)
YZ85(S)
(CDN, AUS, NZ, ZA)YZ85LW (EUROPE)
YZ85LWS (AUS, NZ)
Model code number: YZ85 YZ85LW
5PA7
(USA, CDN, EUROPE,
NZ, ZA)
5PA8
(AUS)5SH7
(EUROPE, NZ)
5SH8
(AUS)
Dimensions: YZ85 YZ85LW
Overall length 1,821 mm (71.7 in) 1,903 mm (74.9 in)
(USA, S, NZ, ZA)
1,818 mm (71.6 in)
(F, D, I, GB, E, CDN,
AUS)
Overall width 758 mm (28.9 in)←
Overall height 1,161 mm (45.7 in) 1,205 mm (47.4 in)
Seat height 864 mm (34.0 in) 904 mm (35.6 in)
Wheelbase 1,258 mm (49.5 in) 1,286 mm (50.6 in)
(USA, S, NZ, ZA)
1,255 mm (49.4 in)
(F, D, I, GB, E, CDN,
AUS)
Minimum ground clearance 351 mm (13.8 in) 393 mm (15.5 in)
Basic weight: YZ85 YZ85LW
With oil and full fuel tank 71 kg (156.5 lb) 73.9 kg (162.9 lb)
Engine:
Engine type Liquid cooled 2-stroke, gasoline
Cylinder arrangement Single cylinder, forward inclined
Displacement 84.7 cm
3 (2.98 Imp oz, 2.86 US oz)
Bore × stroke 47.5 × 47.8 mm (1.870 × 1.882 in)
Compression ratio 8.2 : 1
Starting system Kickstarter
Lubrication system: Premix (30 : 1) (Yamalube 2-R)
Oil type or grade (2-cycle):
Transmission oil Yamalube 4 (10W-30) or SAE 10W-30 type SE
motor oil
Periodic oil change 0.50 L (0.44 Imp qt, 0.52 US qt)
Total amount 0.55 L (0.48 Imp qt, 0.58 US qt)
Coolant capacity (including all routes): 0.54 L (0.48 Imp qt, 0.57 US qt)
Air filter: Wet type element
2

SPEC
2 - 4
MAINTENANCE SPECIFICATIONS
MAINTENANCE SPECIFICATIONS
ENGINE
Item Standard Limit
Cylinder head:
Combustion chamber capacity 7.14 cm
3
(0.25 Imp oz, 0.24 US oz)----
Warp limit ---- 0.03 mm
(0.0012 in)
Cylinder:
Bore size 47.500 ~ 47.514 mm
(1.8701 ~ 1.8706 in)47.6 mm
(1.8740 in)
Taper limit ---- 0.05 mm
(0.0020 in)
Out of round limit ---- 0.01 mm
(0.0004 in)
Piston:
Piston to cylinder clearance 0.040 ~ 0.045 mm
(0.0016 ~ 0.0018 in)0.1 mm
(0.004 in)
Piston size “D”47.457 ~ 47.472 mm
(1.8684 ~ 1.8690 in)----
Measuring point “H”20 mm (0.79 in) ----
Piston off-set 1.0 mm (0.039 in)/EX-side ----
Piston pin bore inside diameter 14.004 ~ 14.015 mm
(0.5513 ~ 0.5518 in)14.040 mm
(0.5528 in)
Piston pin outside diameter 13.996 ~ 14.000 mm
(0.5510 ~ 0.5512 in)13.975 mm
(0.5502 in)
Piston ring:
Type Plain ----
Dimensions (B × T) 0.8 × 2.0 mm (0.031 × 0.079 in) ----
End gap (installed) 0.30 ~ 0.45 mm
(0.012 ~ 0.018 in)0.80 mm
(0.031 in)
Side clearance (installed) 0.030 ~ 0.065 mm
(0.001 ~ 0.003 in)0.1 mm
(0.004 in)
B
T

SPEC
2 - 13
MAINTENANCE SPECIFICATIONS
NOTE:
- marked portion shall be checked for torque tightening after break-in or before each race.Part to be tightened Thread size Q’tyTightening torque
Nm m·kg ft·lb
Nipple (spoke)—64 3 0.3 2.2
Rear wheel sprocket M8 × 1.25 4 42 4.2 30
Rear brake caliper protector M6 × 1.0 1 10 1.0 7.2
Drive chain puller adjust bolt and locknut M8 × 1.25 2 16 1.6 11
Engine mounting:
Engine and frame (front) M10 × 1.25 1 69 6.9 50
Engine and frame (lower) M10 × 1.25 1 69 6.9 50
Pivot shaft and nut M12 × 1.25 1 63 6.3 45
Relay arm and frame M10 × 1.25 1 54 5.4 39
Relay arm and connecting rod M12 × 1.25 1 53 5.3 38
Connecting rod and swingarm M12 × 1.25 1 53 5.3 38
Rear shock absorber and frame M10 × 1.25 1 36 3.6 25
Rear shock absorber and relay arm M10 × 1.25 1 36 3.6 25
Rear frame (upper) M8 × 1.25 1 26 2.6 19
Rear frame (lower) M8 × 1.25 2 16 1.6 11
Swingarm and brake hose holder M5 × 0.8 4 1 0.1 0.7
Drive chain tensioner (upper) M8 × 1.25 1 23 2.3 17
Drive chain tensioner (lower) M6 × 1.0 1 10 1.0 7.2
Drive chain support M8 × 1.25 2 16 1.6 11
Drive chain support cover M6 × 1.0 1 7 0.7 5.1
Seal guard and swingarm M6 × 1.0 2 10 1.0 7.2
Fuel tank M6 × 1.0 2 7 0.7 5.1
Fuel cock M6 × 1.0 2 4 0.4 2.9
Fuel tank bracket and fuel tank M6 × 1.0 4 7 0.7 5.1
Seat set bracket and fuel tank M6 × 1.0 1 7 0.7 5.1
Radiator cover M6 × 1.0 3 4 0.4 2.9
Front fender M6 × 1.0 4 7 0.7 5.1
Rear fender M6 × 1.0 4 7 0.7 5.1
Flap guard M6 × 1.0 2 7 0.7 5.1
Side cover M6 × 1.0 2 7 0.7 5.1
Seat M6 × 1.0 2 7 0.7 5.1
Number plate M6 × 1.0 1 7 0.7 5.1

2 - 15
SPEC
EC220001
GENERAL TORQUE SPECIFICATIONS
This chart specifies torque for standard fasten-
ers with standard I.S.O. pitch threads. Torque
specifications for special components or
assemblies are included in the applicable sec-
tions of this book. To avoid warpage, tighten
multi-fastener assemblies in a crisscross fash-
ion, in progressive stages, until full torque is
reached. Unless otherwise specified, torque
specifications call for clean, dry threads. Com-
ponents should be at room temperature.
A: Distance between flats
B: Outside thread diameter
EC230000
DEFINITION OF UNITS
A
(Nut)B
(Bolt)TORQUE
SPECIFICATION
Nm mkg ftlb
10 mm
12 mm
14 mm
17 mm
19 mm
22 mm6 mm
8 mm
10 mm
12 mm
14 mm
16 mm6
15
30
55
85
1300.6
1.5
3.0
5.5
8.5
134.3
11
22
40
61
94
5PA20050
Unit Read Definition Measure
mm
cmmillimeter
centimeter10
-3 meter
10-2 meterLength
Length
kg kilogram 10
3 gram Weight
N Newton 1 kg
× m/sec
2 Force
Nm
m  kgNewton meter
Meter kilogramN
× m
m
× kgTorque
Torque
Pa Pascal N/m
2Pressure
N/mm Newton per millimeter N/mm Spring rate
L
cm
3 Liter
Cubic centimeter—
—Volume or capacity
Volume or capacity
r/min Revolution per minute—Engine speed
GENERAL TORQUE SPECIFICATIONS/
DEFINITION OF UNITS