Yamaha YZ250F(Z), Owner'S Service Manual

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2-4
MAINTENANCE SPECIFICATIONS
Valve, valve seat, valve guide:
Valve clearance (cold)
IN 0.12–0.17 mm (0.0047–0.0067 in) ----
EX 0.17–0.22 mm (0.0067–0.0087 in) ----
Valve dimensions:
"A" head diameter (IN) 22.9–23.1 mm (0.9016–0.9094 in) ----
"A" head diameter (EX) 24.4–24.6 mm (0.9606–0.9685 in) ----
"B" face width (IN) 2.26 mm (0.089 in) ----
"B" face width (EX) 2.26 mm (0.089 in) ----
"C" seat width (IN) 0.9–1.1 mm (0.0354–0.0433 in) 1.6 mm (0.0630
in)
"C" seat width (EX) 0.9–1.1 mm (0.0354–0.0433 in) 1.6 mm (0.0630
in)
"D" margin thickness (IN) 0.8 mm (0.0315 in) ----
"D" margin thickness (EX) 0.7 mm (0.0276 in) ----
Stem outside diameter (IN) 3.975–3.990 mm (0.1565–0.1571 in) 3.945 mm
(0.1553 in)
Stem outside diameter (EX) 4.460–4.475 mm (0.1756–0.1762 in) 4.430 mm
(0.1744 in)
Guide inside diameter (IN) 4.000–4.012 mm (0.1575–0.1580 in) 4.050 mm
(0.1594 in)
Guide inside diameter (EX) 4.500–4.512 mm (0.1772–0.1776 in) 4.550 mm
(0.1791 in)
Stem-to-guide clearance (IN) 0.010–0.037 mm (0.0004–0.0015 in) 0.08 mm (0.003
in)
Stem-to-guide clearance (EX) 0.025–0.052 mm (0.0010–0.0020 in) 0.10 mm (0.004
in)
Item Standard Limit