Service manual

ManualsBrandsYamaha ManualsScootersXF50W

VALVES AND VALVE SPRINGS

ENG

EAS00239

CHECKING THE VALVES AND VALVE

GUIDES

The following procedure applies to all of the

valves and valve guides.

1.

Measure:

8valve-stem-to-valve-guide clearance

Valve-stem-to-valve-guide clearance =

Valve guide inside diameter a -

Valve stem diameter b

Out of specification -* Replace the valve

guide.

Valve-stem-to-valve-guide clearance

Intake

0.010 ~

0.037

mm(0.0004~0.0015 in)

<Limit>: 0.08 mm(0.0031 in)

Exhaust

0.025

~

0.052

mm(0.001~0.002 in)

<Limit>: 0.10 mm(0.0039 in)

2.

Replace:

8valve guide

NOTE:

To ease valve guide removal and installation,

and to maintain the correct fit, heat the cylinder

head to 100°C (212°F) in an oven.

•••••••••••••••••••••••

a. Remove the valve guide with the valve

guide remover 1.

b. Install the new valve guide with the valve

guide installer 2 and valve guide remover

1.

c. After installing the valve guide, bore the

valve guide with the valve guide reamer 3

to obtain the proper valve-stem-to-valve-

guide clearance.

NOTE:

After replacing the valve

guide,

reface the valve

seat.

Valve guide remover (4.0 mm)

90890-04111(YM-04111)

Valve guide installer (4.0 mm)

90890-04112(YM-04112)

Valve guide reamer (4.0 mm)

90890-04113(YM-04113)

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