Pushrod Inspection (cont.)
Check for straightness by rolling pushrods
across a flat surface, such as glass plate. If
any wobble is detected, replace.
Check overall length with caliper or
micrometer. Length should be 2.453" (62.3
mm). If length is less than 2.449 (62.2),
pushrod should be replaced.
G. Cam Lobe Inspection
Inspect cam lobe/gear for signs of wear,
roughness, burning, and/or damaged teeth.
Measure lobe height with a caliper or
micrometer. Height should be .898" - .910"
(22.85 mm -23.15 mm). If height is less
than .887" (22.5 mm) cam lobe/gear should
be replaced.
H. Locate TDC-Compression Stroke
Valve clearance adjustments should be
performed with piston at top-dead-center (TDC)
of the compression stroke. In this position, the
cam lobe faces straight down and both valves
are closed. To distinguish this crankshaft
position from TDC--exhaust stroke (cam lobe
facing up), follow these simple steps:
STEP 1.
Prepare engine for valve clearance
adjustment by removing cylinder cover and
rocker arm cover.
STEP 2.
Looking down from front of power-
head, rotate crankshaft until left edge of
flywheel magnet cluster aligns with left,
inside edge of clutch drum housing. (If
housing has been removed, align adjacent
flywheel fin with edge of cylinder casting.)
STEP 3.
Rotate flywheel back and forth while
observing rocker arms. If rocker arms move,
piston is at TDC-exhaust. Rotate crankshaft
one complete revolution, again aligning
edge of magnets or flywheel fin as described
above. Now piston should be set at TDC-
compression stroke.
TDC -compression can be determined
without removing rocker arm cover. At TDC-
exhaust (cam lobe up), a noticeable resistance
can be felt when rotating crankshaft back and
forth. At TDC-compression, lobe is down so
there is little or no resistance.
Inspecting
Pushrod &
Cam Lobe
Section
4 Valve Clearance Adjustment
9
Measuring cam lobe height.
Turn crankshaft until left edge of flywheel
magnet cluster aligns with edge of clutch drum
housing (arrow). In this position, piston is at
TDC. Rotate crankshaft back and forth to
determine whether it is TDC-compression or
TDC-exhaust. Adjustments should be made at
TDC-compression.
If clutch drum housing has been removed,
flywheel fin adjacent to left edge of magnet
cluster can be used to locate TDC. When edge
of fin aligns with parallel edge of cylinder
casting (arrows), piston is at TDC.
Locating Top-
Dead-Center,
Compression
Edition 2 • 09/2007
