Engine Service Manual

71
Disassembly/Inspection and Service
32 690 03 Rev. I KohlerEngines.com
Inspection and Service
Valve Details
H
E
F
A
C
D
F
E
G
A
H
D
A
B
B
G
Intake Valve
Exhaust Valve
Intake Insert
Exhaust Insert
Dimension Intake Exhaust
A Seat Angle 89° 89°
B Insert O.D. 36.987/37.013 mm (1.4562/1.4572 in.) 32.987/33.013 mm (1.2987/1.2997 in.)
C Guide Depth 4 mm (0.1575 in.) 6.5 mm (0.2559 in.)
D Guide I.D. 7.040/7.060 mm (0.2772/0.2780 in.) 7.040/7.060 mm (0.2772/0.2780 in.)
E Valve Head Diameter 33.37/33.63 mm (1.3138/1.3240 in.) 29.37/29.63 mm (1.1563/1.1665 in.)
F Valve Face Angle 45° 45°
G Valve Margin (Min.) 1.5 mm (0.0591 in.) 1.5 mm (0.0591 in.)
H Valve Stem Diameter 6.982/7.000 mm (0.2749/0.2756 in.) 6.970/6.988 mm (0.2744/0.2751 in.)
After cleaning, check fl atness of cylinder head and corresponding top surface of crankcase, using a surface plate or
piece of glass and feeler gauge. Maximum allowable out of fl atness is 0.076 mm (0.003 in.).
Carefully inspect valve mechanism parts. Inspect valve
springs and related hardware for excessive wear or
distortion. Check valves and valve seat area or inserts
for evidence of deep pitting, cracks, or distortion.
Check clearance of valve stems in guides. See valve
details and specifi cations.
Hard starting, or loss of power accompanied by high
fuel consumption may be symptoms of faulty valves.
Although these symptoms could also be attributed to
worn rings, remove and check valves fi rst. After removal,
clean valve heads, faces, and stems with a power wire
brush. Then, carefully inspect each valve for defects
such as warped head, excessive corrosion, or worn stem
end. Replace valves found to be in bad condition.
Valve Guides
If a valve guide is worn beyond specifi cations, it will not
guide valve in a straight line. This may result in burnt
valve faces or seats, loss of compression, and excessive
oil consumption.
To check valve guide-to-valve stem clearance,
thoroughly clean valve guide and, using a split-ball
gauge, measure inside diameter of guide. Then, using
an outside micrometer, measure diameter of valve stem
at several points on stem where it moves in valve guide.
Use largest stem diameter to calculate clearance by
subtracting stem diameter from guide diameter. If intake
clearance exceeds 0.040/0.078 mm (0.0016/0.0031 in.)
or exhaust clearance exceeds 0.052/0.090 mm
(0.0020/0.0035 in.), determine whether valve stem or
guide is responsible for excessive clearance.
Maximum (I.D.) wear on intake valve guide is 7.140 mm
(0.2811 in.) while 7.160 mm (0.2819 in.) is maximum
allowed on exhaust guide. Guides are not removable but
can be reamed 0.25 mm (0.010 in.) oversize. Valves with
0.25 mm oversize stems must then be used.
If guides are within limits but valve stems are worn
beyond limits, install new valves.