Inspection Of Valve; Inspection Of Valve Guide - TOHATSU MFS 60A Service Manual

Power Unit

10) Inspection of Valve

1. Check valve for dent and wear on the face. Replace if
necessary.
Measure valve stem outer diameter a . Replace if the
2.
diameter is less than specified value.
Valve Stem Outer Diameter a : Standard Value
Intake Side : 5.48 mm (0.216 in)
Exhaust Side : 5.46 mm (0.215 in)
Functional Limit :
Intake Side : 5.46 mm (0.215 in)
Exhaust Side : 5.44 mm (0.214 in)
3. Measure valve stem runout. Replace if the runout is over
specified value.
Valve Stem Runout Limit :
Intake Side : 0.07 mm (0.0028 in)
Exhaust Side : 0.05 mm (0.0020 in)

11) Inspection of Valve Guide

Before inspecting valve guide, check that valve
stem outer diameter is within specified range.
Measure valve guide inner diameter a . Replace cylinder
1.
head if the inner diameter is over specified value.
Valve Guide Inner Diameter a : Standard Value
Intake/Exhaust Side : 5.51 mm (0.217 in)
Functional Limit :
Intake Side : 5.55 mm (0.0218 in)
Exhaust Side : 5.57 mm (0.0219 in)
2. Obtain clearance between valve guide and valve stem by
calculating as described below. Replace cylinder head and/
or valve if the clearance is over specified value.
Clearance between Valve Guide and Valve Stem =
Valve Guide Inner Diameter a – Valve Stem Outer Diameter b :
Intake Side : 0.008 to 0.040 mm ( 0.00031 to 0.00157 in)
Exhaust Side : 0.025 to 0.057 mm (0.00098 to 0.00224 in )
Functional Limit :
Intake Side : 0.070 mm (0.00276 in)
Exhaust Side : 0.100 mm (0.00394 in)
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a
a
b
4st 60 2019