2001 YAMAHA WR 426F maintenance

2 - 7
SPEC

MAINTENANCE SPECIFICATIONS (WR426F)
Piston rings:
Top ring
Type Barrel ----
Dimensions (B

´

T) 1.2
´
3.5 mm (0.05
´
0.14 in) ----
End gap (installed) 0.20 ~ 0.30 mm
(0.008 ~ 0.012 in)0.55 mm
(0.022 in)
Side clearance (installed) 0.030 ~ 0.065 mm
(0.0012 ~ 0.0026 in)0.12 mm
(0.005 in)
2nd ring
Type Taper ----
Dimensions (B

´

T) 1.00
´
3.35 mm (0.04
´
0.13 in) ----
End gap (installed) 0.35 ~ 0.50 mm
(0.014 ~ 0.020 in)0.85 mm
(0.033 in)
Side clearance 0.020 ~ 0.055 mm
(0.0008 ~ 0.0022 in)0.12 mm
(0.005 in)
Oil ring
Dimensions (B

´

T) 2.0
´
2.9 mm (0.08
´
0.11 in) ----
End gap (installed) 0.2 ~ 0.5 mm (0.01 ~ 0.02 in) ----
Crankshaft:
Crank width “A” 61.95 ~ 62.00 mm
(2.439 ~ 2.441 in)----
Runout limit “C” 0.03 mm (0.0012 in) 0.05 mm
(0.002 in)
Big end side clearance “D” 0.15 ~ 0.45 mm
(0.0059 ~ 0.0177 in)0.50 mm
(0.02 in)
Small end free play “F” 0.4 ~ 1.0 mm (0.02 ~ 0.04 in) 2.0 mm
(0.08 in)
Balancer:
Balancer drive method Gear ----
Decompression device:
Type Manual ----
Cable free play 5 ~ 9 mm (0.20 ~ 0.35 in)
Air filter oil grade: Engine oil ----Item Standard Limit
T
B
B
T
B
T

2 - 8
SPEC

MAINTENANCE SPECIFICATIONS (WR426F)
Clutch:
Friction plate thickness 2.9 ~ 3.1 mm (0.114 ~ 0.122 in) 2.7 mm
(0.106 in)
Quantity 9 ----
Clutch plate thickness 1.1 ~ 1.3 mm (0.043 ~ 0.051 in) ----
Quantity 8 ----
Warp limit ---- 0.1 mm
(0.004 in)
Clutch spring free length 48.4 mm (1.91 in) 47.4 mm
(1.87 in)
Quantity 6 ----
Clutch housing thrust clearance 0.10 ~ 0.35 mm
(0.0039 ~ 0.0138 in)----
Clutch housing radial clearance 0.010 ~ 0.044 mm
(0.0004 ~ 0.0017 in)----
Clutch release method Inner push, cam push ----
Shifter:
Shifter type Cam drum and guide bar ----
Guide bar bending limit ---- 0.05 mm
(0.002 in)
Kick starter:
Type Ratchet type ----
Carburetor:
USAEUROPE,
CDN, AUS, NZ,
ZA
I. D. mark 5NG1 00 5NG2 10 ----
Main jet (M.J) #165
¬
----
Main air jet (M.A.J) #200
¬
----
Jet needle-clip position (J.N) OBDRR-4 OBDQR-4 ----
Cutaway (C.A) 1.5
¬
----
Pilot jet (P.J) #42
¬
----
Pilot air jet (P.A.J) #75
¬
----
Pilot outlet (P.O) ø0.9
¬
----
Pilot screw (example) (P.S) 1-5/8 7/8 ----
Bypass (B.P) ø1.0
¬
----
Valve seat size (V.S) ø3.8
¬
----
Starter jet (G.S) #65
¬
----
Float height (F.H) 8 mm (0.31 in)
¬
----
Engine idle speed 1,700 ~
1,900 r/min
¬
----
Intake vacuum 33.3 ~ 38.7 kPa
(250 ~ 290 mmHg,
9.84 ~ 11.42 inHg)
¬
---- Item Standard Limit

2 - 9
SPEC

MAINTENANCE SPECIFICATIONS (WR426F)
Lubrication system:
Oil filter type Wire mesh type ----
Oil pump type Trochoid type ----
Tip clearance “A” 0.12 mm or less
(0.0047 in or less)0.20 mm
(0.008 in)
Tip clearance “B” 0.09 ~ 0.17 mm
(0.0035 ~ 0.0067 in)0.24 mm
(0.009 in)
Side clearance 0.03 ~ 0.10 mm
(0.0012 ~ 0.0039 in)0.17 mm
(0.007 in)
Bypass valve setting pressure 40 ~ 80 kPa (0.4 ~ 0.8 kg/cm
2

,
5.69 ~ 11.38 psi)----
Cooling:
Radiator core size
Width 117.8 mm (4.6 in) ----
Height 260 mm (10.2 in) ----
Thickness 32 mm (1.26 in) ----
Radiator cap opening pressure110 kPa (1.1 kg/cm
2

, 15.6 psi)----
Radiator capacity (total) 0.76 L (0.67 lmp qt, 0.80 US qt) ----
Water pump
Type Single-suction centrifugal pump ----Item Standard Limit

2 - 10
SPEC

MAINTENANCE SPECIFICATIONS (WR426F)
Item Standard
Lubrication chart:
Pressure feed
Splashed scavenge
Oil strainer
Oil pan Oil pump rotor 2
Oil pump rotor 1
Oil tank
Oil filter
Check ball
Cylinder head
Crank pinPiston pinPiston
Drive axleMain axleTransmission gears
Camshaft
Valve lifter

2 - 11
SPEC

MAINTENANCE SPECIFICATIONS (WR426F)
Part to be tightened Thread size Q’tyTightening torque
Nm m·kg ft·lb
Spark plug M10S
´
1.0 1 13 1.3 9.4
Camshaft cap M6
´
1.0 10 10 1.0 7.2
Cylinder head (stud bolt) M6
´
1.0 2 7 0.7 5.1
M8
´
1.25 3 15 1.5 11
(bolt) M10
´
1.25 4 44 4.4 32
(nut) M6
´
1.0 2 10 1.0 7.2
M8
´
1.25 2 20 2.0 14
Cylinder head cover M6
´
1.0 2 10 1.0 7.2
Cylinder M6
´
1.0 1 10 1.0 7.2
Timing chain tensioner M6
´
1.0 2 10 1.0 7.2
Tensioner cap bolt M6
´
1.0 1 7 0.7 5.1
Timing chain guide (rear) M6
´
1.0 2 10 1.0 7.2
Decompression shaft M6
´
1.0 1 7 0.7 5.1
Decompression cable guide M6
´
1.0 1 10 1.0 7.2
Exhaust pipe (nut) M8
´
1.25 1 13 1.3 9.4
(bolt) M8
´
1.25 1 24 2.4 17
Silencer M8
´
1.25 2 35 3.5 25
Silencer clamp M8
´
1.25 1 20 2.0 14
Exhaust pipe protector M6
´
1.0 3 10 1.0 7.2
Spark arrester (for USA) M6
´
1.0 3 10 1.0 7.2
Silencer end pipe (for USA) M6
´
1.0 1 10 1.0 7.2
Clamp (air cleaner joint) M5
´
0.8 1 3 0.3 2.2
Clamp (carburetor joint) M4
´
0.7 1 3 0.3 2.2
Air filter joint clamp M6
´
1.0 1 3 0.3 2.2
Throttle cable cover M5
´
0.8 1 4 0.4 2.9
Air filter element M6
´
1.0 1 2 0.2 1.4
Air filter case cover M6
´
1.0 4 4 0.4 2.9
Radiator panel (upper) M6
´
1.0 2 10 1.0 7.2
Radiator M6
´
1.0 6 10 1.0 7.2
Radiator hose clamp M6
´
1.0 8 2 0.2 1.4
Impeller M8
´
1.25 1 14 1.4 10
Water pump housing cover M6
´ 1.0 3 10 1.0 7.2
Coolant drain bolt M6 ´ 1.0 1 10 1.0 7.2
Oil pump cover M5 ´ 0.8 1 4 0.4 2.9
Oil pump M6 ´ 1.0 3 10 1.0 7.2
Engine oil drain bolt (oil filter) M6 ´ 1.0 1 10 1.0 7.2
Oil filter cover M6 ´ 1.0 2 10 1.0 7.2
Oil delivery pipe 1 M10 ´ 1.25
M8 ´ 1.251
220
182.0
1.814
13
Oil hose clamp — 2 2 0.2 1.4
Clutch cover M6 ´ 1.0 7 10 1.0 7.2
Crankcase cover (right) M6 ´ 1.0 10 10 1.0 7.2
Crankcase cover (left) M6 ´ 1.0 8 10 1.0 7.2
Crankcase M6 ´ 1.0 12 12 1.2 8.7

2 - 12
SPECMAINTENANCE SPECIFICATIONS (WR426F)
Oil drain bolt (crankcase) M12 ´ 1.5 1 20 2.0 1.4
Oil drain bolt (frame) M8 ´ 1.25 1 23 2.3 17
Oil strainer (frame) M18 ´ 1.5 1 90 9.0 65
Crankcase bearing stopper M6 ´ 1.0 15 10 1.0 7.2
Drive axle oil seal stopper M6 ´ 1.0 2 10 1.0 7.2
Ratchet wheel guide M6 ´ 1.0 2 12 1.2 8.7
Kick crank M8 ´ 1.25 1 33 3.3 24
Primary drive gear M20 ´ 1.0 1 75 7.5 54
Clutch boss M20 ´ 1.0 1 75 7.5 54
Clutch spring M6 ´ 1.0 6 8 0.8 5.8
Balancer driven gear M14 ´ 1.0 1 50 5.0 36
Balancer weight plate M6 ´ 1.0 3 10 1.0 7.2
Drive sprocket M20 ´ 1.0 1 75 7.5 54
Shift guide M6 ´ 1.0 2 10 1.0 7.2
Stopper lever M6 ´ 1.0 1 10 1.0 7.2
Segment M8 ´ 1.25 1 30 3.0 22
Neutral switch M5 ´ 0.8 2 4 0.4 2.9 Part to be tightened Thread size Q’tyTightening torque
Nm m·kg ft·lb
NOTE:
- marked portion shall be checked for torque tightening after break-in or before each race.

2 - 13
SPECMAINTENANCE SPECIFICATIONS (WR426F)
EC212201
CHASSIS
Item Standard Limit
Steering system:
Steering bearing type Taper roller bearing ----
Front suspension: USA, CDN
AUS, NZ, ZAEUROPE
Front fork travel 300 mm
(11.8 in)¬----
Fork spring free length 460 mm
(18.1 in)¬455 mm (17.9 in)
Spring rate, STD K = 4.51 N/mm
(0.46 kg/mm,
25.8 lb/in)K = 4.12 N/mm
(0.42 kg/mm,
23.5 lb/in)----
Optional spring/spacer Yes¬----
Oil capacity 573 cm
3
(20.2 lmp oz,
19.4 US oz) 583 cm3
(20.5 lmp oz,
19.7 US oz)----
Oil level 135 mm
(5.31 in)125 mm
(4.92 in)----

(From top of outer tube with inner
tube and damper rod fully com-
pressed without spring.)80 ~ 150 mm
(3.15 ~ 5.91 in)¬----
Oil grade Suspension oil
“01”¬----
Inner tube outer diameter 46 mm (1.81 in)¬----
Front fork top end Zero mm
(Zero in)¬----
Rear suspension: USA, CDN,
AUS, NZ, ZAEUROPE
Shock absorber travel 132 mm
(5.20 in)¬----
Spring free length 260 mm
(10.24 in)¬----
Fitting length 241 mm
(9.49 in)244 mm
(9.61 in)----
240.5 ~ 258.5 mm
(9.47 ~ 10.18 in)¬----
Spring rate, STD K = 49.0 N/mm
(5.00 kg/mm,
280.0 lb/in)K = 47.0 N/mm
(4.80 kg/mm,
268.8 lb/in)----
Optional spring Yes¬----
Enclosed gas pressure 1,000 kPa
(10 kg/cm
2,
142 psi)¬----
Swingarm:
Swingarm free play limit
End ---- 1.0 mm (0.04 in)

2 - 14
SPECMAINTENANCE SPECIFICATIONS (WR426F)
Wheel:
Front wheel type Spoke wheel ----
Rear wheel type Spoke wheel ----
Front rim size/material 21 ´ 1.60/Aluminum ----
Rear rim size/material 18 ´ 2.15/Aluminum ----
Rim runout limit
Radial ---- 2.0 mm (0.08 in)
Lateral ---- 2.0 mm (0.08 in)
Drive chain:
Type/manufacturer DID520VM/DAIDO ----
Number of links 113 links + joint ----
Chain slack 40 ~ 50 mm (1.6 ~ 2.0 in) ----
Chain length (10 links) ----150.1 mm (5.91 in)
Front disc brake:
Disc outside diameter ´ Thickness 250 ´ 3.0 mm (9.84 ´ 0.12 in) 250 ´ 2.5 mm
(9.84 ´ 0.10 in)
Pad thickness 4.4 mm (0.17 in) 1 mm (0.04 in)
Master cylinder inside dia. 11.0 mm (0.433 in) ----
Caliper cylinder inside dia. 27.0 mm (1.063 in) ´ 2 ----
Brake fluid type DOT #4 ----
Rear disc brake:
Disc outside diameter ´ Thickness 240 ´ 4.0 mm (9.45 ´ 0.16 in) 240 ´ 3.5 mm
(9.45 ´ 0.14 in)
Deflection limit ----0.15 mm (0.006 in)
Pad thickness 6.4 mm (0.25 in) 1.0 mm (0.04 in)
Master cylinder inside dia. 12.7 mm (0.500 in) ----
Caliper cylinder inside dia. 27.0 mm (1.063 in) ´ 1 ----
Brake fluid type DOT #4 ----
Brake lever and brake pedal:
Brake lever position 95 mm (3.74 in) ----
Brake pedal height
(vertical height below footrest top)5 mm (0.20 in) ----
Clutch lever free play (at lever pivot) 2 ~ 4 mm (0.08 ~ 0.16 in) ----
Throttle grip free play 3 ~ 5 mm (0.12 ~ 0.20 in) ----Item Standard Limit