Yamaha YZ 2017 Series Owner's Service Manual page 45

Valve spring
Free length (intake)
Limit
Free length (exhaust)
Limit
Installed length (intake)
Installed length (exhaust)
Spring rate K1 (intake)
Spring rate K2 (intake)
Spring rate K1 (exhaust)
Spring rate K2 (exhaust)
Installed compression spring force (intake)
Installed compression spring force (exhaust)
Spring tilt (intake)
Spring tilt (exhaust)
Winding direction (intake)
Winding direction (exhaust)
Cylinder
Bore
Taper limit
Out of round limit
Piston
Piston-to-cylinder clearance
Limit
Diameter
Measuring point (from piston skirt bottom)
Offset
Piston pin bore inside diameter
Limit
Piston pin outside diameter
Limit
Piston ring
Top ring
Ring type
Dimensions (B  T)
End gap (installed)
Limit
Ring side clearance
Limit
Oil ring
Dimensions (B  T)
End gap (installed)
ENGINE SPECIFICATIONS
39.03 mm (1.54 in)
37.08 mm (1.46 in)
35.59 mm (1.40 in)
33.81 mm (1.33 in)
32.50 mm (1.28 in)
29.60 mm (1.17 in)
25.56 N/mm (2.61 kgf/mm, 145.95 lbf/in)
37.83 N/mm (3.86 kgf/mm, 216.01 lbf/in)
24.53 N/mm (2.50 kgf/mm, 140.07 lbf/in)
31.99 N/mm (3.26 kgf/mm, 182.66 lbf/in)
155.00–179.00 N (15.81–18.25 kgf,
34.84–40.24 lbf)
137.00–157.00 N (13.97–16.01 kgf,
30.80–35.29 lbf)
1.7 mm (0.07 in)
1.6 mm (0.06 in)
Clockwise
Clockwise
77.000–77.010 mm (3.0315–3.0319 in)
0.050 mm (0.0020 in)
0.050 mm (0.0020 in)
0.030–0.055 mm (0.0012–0.0022 in)
0.15 mm (0.006 in)
76.955–76.970 mm (3.0297–3.0303 in)
4.0 mm (0.16 in)
0.00 mm (0.0000 in)
16.002–16.013 mm (0.6300–0.6304 in)
16.043 mm (0.6316 in)
15.991–16.000 mm (0.6296–0.6299 in)
15.971 mm (0.6288 in)
Barrel
0.90  2.70 mm (0.04  0.11 in)
0.15–0.25 mm (0.0059–0.0098 in)
0.50 mm (0.0197 in)
0.030–0.065 mm (0.0012–0.0026 in)
0.115 mm (0.0045 in)
1.50  2.25 mm (0.06  0.89 in)
0.10–0.35 mm (0.0039–0.0138 in)
2-4