Yamaha YZF-R25, Service Manual

Page: 37 / 456

ENGINE SPECIFICATIONS
2-4
Limit 4.550 mm (0.1791 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)
Valve spring
Free length (intake) 37.58 mm (1.48 in)
Limit 35.70 mm (1.41 in)
Free length (exhaust) 37.58 mm (1.48 in)
Limit 35.70 mm (1.41 in)
Installed length (intake) 30.90 mm (1.22 in)
Installed length (exhaust) 30.90 mm (1.22 in)
Spring rate K1 (intake) 25.68 N/mm (2.62 kgf/mm, 146.63 lbf/in)
Spring rate K2 (intake) 40.50 N/mm (4.13 kgf/mm, 231.26 lbf/in)
Spring rate K1 (exhaust) 25.68 N/mm (2.62 kgf/mm, 146.63 lbf/in)
Spring rate K2 (exhaust) 40.50 N/mm (4.13 kgf/mm, 231.26 lbf/in)
Installed compression spring force (intake) 159.60–183.60 N (16.27–18.72 kgf, 35.88–
41.27 lbf)
Installed compression spring force (exhaust) 159.60–183.60 N (16.27–18.72 kgf, 35.88–
41.27 lbf)
Spring tilt (intake) 1.6 mm (0.06 in)
Spring tilt (exhaust) 1.6 mm (0.06 in)
Winding direction (intake) Clockwise
Winding direction (exhaust) Clockwise
Cylinder
Bore 60.000–60.010 mm (2.3622–2.3626 in)
Taper limit 0.050 mm (0.0020 in)
Out of round limit 0.050 mm (0.0020 in)
Piston
Piston-to-cylinder clearance 0.015–0.048 mm (0.0006–0.0019 in)
Diameter 59.962–59.585 mm (2.3607–2.3459 in)
Measuring point (from piston skirt bottom) 7.0 mm (0.28 in)
Offset **
Piston pin bore inside diameter 15.002–15.013 mm (0.5906–0.5911 in)
Limit 15.043 mm (0.5922 in)
Piston pin outside diameter 14.995–15.000 mm (0.5904–0.5906 in)
Limit 14.975 mm (0.5896 in)
Piston-pin-to-piston-pin-bore clearance 0.009–0.025 mm (0.0004–0.0010 in)
Limit 0.075 mm (0.0030 in)
Piston ring
Top ring
Ring type Barrel
End gap (installed) 0.10–0.25 mm (0.0039–0.0098 in)
Limit 0.40 mm (0.0157 in)
Ring side clearance 0.030–0.065 mm (0.0012–0.0026 in)
Limit 0.100 mm (0.0039 in)