Yamaha YZ 2018 Series, Owner'S Service Manual, Page: 44 / 402

ENGINE SPECIFICATIONS
2-3
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)
Limit 0.080 mm (0.0032 in)
Camshaft lobe dimensions
Lobe height (Intake) 31.830–31.930 mm (1.2531–1.2571 in)
Limit 31.730 mm (1.2492 in)
Lobe height (Exhaust) 33.870–33.970 mm (1.3335–1.3374 in)
Limit 33.770 mm (1.3295 in)
Camshaft runout limit 0.030 mm (0.0012 in)
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 seat contact width (intake) 0.90–1.10 mm (0.0354–0.0433 in)
Limit 1.6 mm (0.06 in)
Valve seat contact width (exhaust) 0.90–1.10 mm (0.0354–0.0433 in)
Limit 1.6 mm (0.06 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)
Valve guide inside diameter (exhaust) 4.500–4.512 mm (0.1772–0.1776 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)
Valve spring
Free length (intake) 39.03 mm (1.54 in)
Limit 37.08 mm (1.46 in)
Free length (exhaust) 35.59 mm (1.40 in)
Limit 33.81 mm (1.33 in)
Spring tilt (intake) 1.7 mm (0.07 in)
Spring tilt (exhaust) 1.6 mm (0.06 in)
Cylinder
Bore 77.000–77.010 mm (3.0315–3.0319 in)
Wear limit 77.060 mm (3.0339 in)
Piston
Piston-to-cylinder clearance 0.030–0.055 mm (0.0012–0.0022 in)
Diameter 76.955–76.970 mm (3.0297–3.0303 in)
Measuring point (from piston skirt bottom) 4.0 mm (0.16 in)
Piston pin bore inside diameter 16.002–16.013 mm (0.6300–0.6304 in)
Limit 16.043 mm (0.6316 in)
Piston pin outside diameter 15.991–16.000 mm (0.6296–0.6299 in)
Limit 15.971 mm (0.6288 in)
Piston-pin-to-piston-pin-bore clearance 0.002–0.022 mm (0.0001–0.0009 in)