Specifications

44
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VALVE SPRING FREE LENGTH
Measure the free length of the valve
springs.
MODEL STANDARD
(MM)
SERVICE
LIMIT (MM)
DW168 30 ~ 31 29.0
DW177 38.5 ~ 39.5 37.5
DW188 38.5 ~ 39.5 37.5
NOTE: Replace the springs if they are
shorter than the service limit.
VALVE SEAT WIDTH
Measure the valve seat width.
MODEL STANDARD
(MM)
SERVICE
LIMIT (MM)
DW168 0.7 ~ 0.9 2.0
DW177 0.7 ~ 0.9 2.0
DW188 0.7 ~ 0.9 2.0
NOTE: Recondition the valve seat if the
width is under the standard or over the
service limit.
CYLINDER HEAD
WARNING: Always wear certified safety equipment: ANSI Z87.1 eye protection (CAN/
CSA Z94.3) with side shields when removing carbon deposits.
WARNING: To reduce the possibility of fire or explosion, be careful when working around
gasoline. Use only a nonflammable solvent, not gasoline, to clean parts. Keep smoking
products, sparks and flames away from all fuel related parts.
 • Remove carbon deposits from
STRAIGHT
EDGE
FEELER
GAUGE
combustion chamber using a wire
brush.
 • Remove any gasket material from
cylinder head surface.
 • Checkthespark plug holeandvalve
areasforcracks.
 • Checkthe cylinderhead forwarpage
with a straight edge and a feeler
gauge.
STANDARD
(MM)
SERVICE LIMIT
(MM)
0 0.10
VALVE STEM O. D.
Inspect each valve for:
 • surfaceirregularities
 • bending
 • stemwear
Replace valve if needed.
Measure and record each valve stem O. D.
modeL
Standard
(mm)
Service
Limit
(mm)
dW168
IN
5.468~5.48 5.318
EX
5.418~5.44 5.275
dW177
IN
6.568~6.580 6.440
EX
6.545~6.560 6.400
dW188
IN
6.568~6.580 6.440
EX
6.545~6.560 6.400
NOTE: Replace the valves if the O. D. is smaller than the service limit.
VALVE GUIDE I. D.
NOTE: ream the valve guides to remove any
carbon deposits before measuring.
Measure and record each valve guide I. D.
MODEL
STANDARD
(MM)
SERVICE
LIMIT
(MM)
dW168
5.500~5.512 5.572
dW177
6.600~6.615 6.660
dW188
6.600~6.615 6.660
NOTE: Replace the valve guides if the I. D. Is
over the service limit.
GUIDE TO STEM CLEARANCE
Subtract each valve stem O. D. from the
corresponding guide I. D. to obtain the
stem to guide clearance.
MODEL
STANDARD
(MM)
SERVICE
LIMIT
(MM)
dW168
IN
0.020~0.044 0.10
EX
0.060~0.084 0.12
dW177
IN
0.020~0.070 0.11
EX
0.040~0.070 0.15
dW188
IN
0.020~0.070 0.11
EX
0.040~0.070 0.15
CALIPER
VALVE
SEAT
MICROMETER
REAMING TOOL
VALVE
GUIDE
DIAL INDICATOR
BORE GAUGE