Yamaha WR250F(D) Owner's Service Manual

Contents

5-16CAMSHAFTSREMOVING THE CAMSHAFT1. Remove:• Timing mark accessing screw "1"• Crankshaft end accessing screw"2"2. Align:• T.D.C. markWith align mark.Checking steps:a. Turn the crankshaft counterclock-wise with a wrench.b. Align the T.D.C. mark "a" on therotor with the align mark "b" on thecrankcase cover when piston is atT.D.C. on compression stroke.In order to be sure that the piston is atTop Dead Center, the punch mark "c"on the exhaust camshaft and thepunch mark "d" on the intake cam-shaft must align with the cylinderhead surface, as shown in the illustra-tion.3. Remove:• Timing chain tensioner cap bolt"1"• Timing chain tensioner "2"• Gasket4. Remove:• Bolt (camshaft cap) "1"• Camshaft cap "2"• ClipRemove the bolts (camshaft cap) in acrisscross pattern, working from theoutside in.The bolts (camshaft cap) must beremoved evenly to prevent dam-age to the cylinder head, cam-shafts or camshaft caps.5. Remove:• Exhaust camshaft "1"• Intake camshaft "2"Attach a wire "3" to the timing chain toprevent it from falling into the crank-case.CHECKING THE CAMSHAFT1. Inspect:• Cam lobePitting/scratches/blue discolor-ation → Replace.2. Measure:• Cam lobe length "a" and "b"Out of specification → Replace.3. Measure:• Runout (camshaft)Out of specification → Replace.Cam lobes length:Intake "a":29.65–29.75 mm(1.1673–1.1713 in):29.55 mm (1.1634 in)Intake "b":22.45–22.55 mm(0.8839–0.8878 in):22.35 mm (0.8799 in)Exhaust "a":30.399–30.499 mm(1.1968–1.2007 in):30.299 mm (1.1929 in)Exhaust "b":22.45–22.55 mm(0.8839–0.8878 in):22.35 mm (0.8799 in)Runout (camshaft):Less than 0.03 mm(0.0012 in)