Yamaha YZ 2015 Series Owner's Service Manual page 47

Valve face width B (intake)
Valve face width B (exhaust)
Valve seat width C (intake)
Valve seat width C (exhaust)
Valve margin thickness D (intake)
Valve margin thickness D (exhaust)
Valve stem diameter (intake)
Limit
Valve stem diameter (exhaust)
Limit
Valve guide inside diameter (intake)
Limit
Valve guide inside diameter (exhaust)
Limit
Valve-stem-to-valve-guide clearance (intake)
Limit
Valve-stem-to-valve-guide clearance (exhaust)
Limit
Valve stem runout
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)
B
C
D
2-4
ENGINE SPECIFICATIONS
1.697 mm (0.0668 in)
1.909 mm (0.0752 in)
0.90–1.10 mm (0.0354–0.0433 in)
0.90–1.10 mm (0.0354–0.0433 in)
1.20 mm (0.0472 in)
0.85 mm (0.0335 in)
4.975–4.990 mm (0.1959–0.1965 in)
4.945 mm (0.1947 in)
4.460–4.475 mm (0.1756–0.1762 in)
4.430 mm (0.1744 in)
5.000–5.012 mm (0.1969–0.1973 in)
5.050 mm (0.1988 in)
4.500–4.512 mm (0.1772–0.1776 in)
4.550 mm (0.1791 in)
0.010–0.037 mm (0.0004–0.0015 in)
0.080 mm (0.0032 in)
0.025–0.052 mm (0.0010–0.0020 in)
0.100 mm (0.0039 in)
0.010 mm (0.0004 in)
36.69 mm (1.44 in)
35.69 mm (1.41 in)
34.86 mm (1.37 in)
33.86 mm (1.33 in)
31.40 mm (1.24 in)
28.50 mm (1.12 in)
29.65 N/mm (3.02 kgf/mm, 169.30 lbf/in)
39.31 N/mm (4.01 kgf/mm, 224.46 lbf/in)
23.11 N/mm (2.36 kgf/mm, 131.96 lbf/in)
30.88 N/mm (3.15 kgf/mm, 176.32 lbf/in)
146.00–168.00 N (14.89–17.13 kgf,
32.82–37.77 lbf)
137.00–157.00 N (13.97–16.01 kgf,
30.80–35.29 lbf)