Valve Guide Replacement - Honda Metropolitan CHF50 Service Manual

CYLINDER HEAD/VALVES
Inspect and reface
the valve seats
whenever the valve
guides are replaced
(page 8-13).
Ream the valve guide to remove any carbon build
up before measuring the guide.
Insert the reamer from the combustion chamber
side of the head and always rotate the reamer clock-
wise.
REAMER
TOOL:
Valve guide reamer, 4.5 mm 07HMH-ML00101 or
07HMH-ML0010B or
07HMH-ML0010A
(U.S.A. only)
Measure each valve guide I.D. and record it.
SERVICE LIMIT: IN/EX:4.54 mm (0.179 in)
Subtract each valve stem O.D. from the correspond-
ing guide I.D. to obtain the stem-to-guide clearance.
SERVICE LIMIT:
IN: 0.075 mm (0.0030 in)
EX: 0.085 mm (0.0033 in)
If the stem-to-guide clearance exceeds the service
limit, determine if a new guide with standard
dimensions would bring the clearance within toler-
ance.
If so, replace any guides as necessary and ream to
fit.
If the stem-to-guide clearance exceeds the service
limit with new guide, also replace the valve.
CAM CHAIN TENSIONER/GUIDE
Check the tensioner and guide for excessive wear or
damage.
If necessary replacement in the following proce-
dure.
Remove the oil pump driver gear (page 4-4).
Remove the dowel pin and cam chain tensioner.
Remove the cam chain guide from the cylinder and
crankcase grooves.
Remove the cam chain.
Installation is in the reverse order of removal.
VALVE GUIDE REPLACEMENT
Be sure to wear
heavy gloves to
avoid burns when
handling the heated
cylinder head.
Using a torch to
heat the cylinder
head may cause
warpage.
Chill the valve guides in a freezer for about 1 hour.
Heat the cylinder head to 130 °C - 140 °C (275 °F -
290 °F) with a hot plate or oven. Do not heat the cyl-
inder head beyond 150 °C (300 °F). Use temperature
indicator sticks, available from welding supply
stores, to be sure the cylinder head is heated to the
proper temperature.
Support the cylinder head and drive the valve
guides out of the cylinder head from the combus-
tion chamber side.
VALVE GUIDE DRIVER
TOOL:
Valve guide driver, 4.5 mm 07HMD-ML00101
8-13