Yamaha YZ 2017 Series, Owner'S Service Manual, Page: 44 / 410

ENGINE SPECIFICATIONS
2-3
Spark plug(s)
Manufacturer/model NGK/LMAR8G
Spark plug gap 0.7–0.8 mm (0.028–0.031 in)
Cylinder head
Combustion chamber volume 12.07–12.87 cm
3
(0.74–0.79 cu.in)
Warpage limit 0.05 mm (0.0020 in)
Camshaft
Drive system Chain drive (left)
Camshaft cap inside diameter 22.000–22.021 mm (0.8661–0.8670 in)
Camshaft journal diameter 21.959–21.972 mm (0.8645–0.8650 in)
Camshaft-journal-to-camshaft-cap clearance 0.028–0.062 mm (0.0011–0.0024 in)
Camshaft lobe dimensions
Lobe height (Intake) 31.830–31.930 mm (1.2531–1.2571 in)
Limit 31.730 mm (1.2492 in)
Base circle diameter (Intake) 22.450–22.550 mm (0.8839–0.8878 in)
Limit 22.350 mm (0.8799 in)
Lobe height (Exhaust) 33.870–33.970 mm (1.3335–1.3374 in)
Limit 33.770 mm (1.3295 in)
Base circle diameter (Exhaust) 25.211–25.311 mm (0.9926–0.9965 in)
Limit 25.111 mm (0.9886 in)
Camshaft runout limit 0.030 mm (0.0012 in)
Timing chain
Tensioning system Automatic
Valve, valve seat, valve guide
Valve clearance (cold)
Intake 0.12–0.19 mm (0.0047–0.0075 in)
Exhaust 0.17–0.24 mm (0.0067–0.0094 in)
Valve dimensions
Valve head diameter (intake) 30.90–31.10 mm (1.2165–1.2244 in)
Valve head diameter (exhaust) 24.90–25.10 mm (0.9803–0.9882 in)
Valve face width (intake) 1.697 mm (0.0668 in)
Valve face width (exhaust) 1.909 mm (0.0752 in)
Valve seat contact width (intake) 0.90–1.10 mm (0.0354–0.0433 in)
Valve seat contact width (exhaust) 0.90–1.10 mm (0.0354–0.0433 in)
Valve margin thickness (intake) 1.20 mm (0.0472 in)
Valve margin thickness (exhaust) 0.85 mm (0.0335 in)
Valve stem diameter (intake) 4.975–4.990 mm (0.1959–0.1965 in)
Limit 4.945 mm (0.1947 in)
Valve stem diameter (exhaust) 4.460–4.475 mm (0.1756–0.1762 in)
Limit 4.430 mm (0.1744 in)
Valve guide inside diameter (intake) 5.000–5.012 mm (0.1969–0.1973 in)
Limit 5.050 mm (0.1988 in)
Valve guide inside diameter (exhaust) 4.500–4.512 mm (0.1772–0.1776 in)
Limit 4.550 mm (0.1791 in)
Valve-stem-to-valve-guide clearance (intake) 0.010–0.037 mm (0.0004–0.0015 in)
Limit 0.080 mm (0.0032 in)
Valve-stem-to-valve-guide clearance (exhaust) 0.025–0.052 mm (0.0010–0.0020 in)
Limit 0.100 mm (0.0039 in)
Valve stem runout 0.010 mm (0.0004 in)