Kohler K91 Service Manual page 106

Measuring Piston-to-Bore Cleara nce
Before i nstal ling the piston i nto the cylinder bore , it
is necessary that the clearance be accurately
checked . This step is often overlooked , and if the
clearances are not within specifications , generally
engine failure will result .
NOTE : Do not use a feeler gauge to measure pis­
ton-to-bore clearance , it will yield inaccurate
measurements. Use a micrometer .
The following procedures should be used to accu­
rately measure the piston-to-bore clearance :
1 . Use a m icrometer and measure the d iameter
of the piston as shown in Figure 1 1 -4 .
o
Style
Style
A-Measu re p i ston d i a meter ( 0 1 ) perpend i c u l a r
t o p i ston p i n j ust below t h e o i l r i n g g roove.
0 1
1 /2"
01
Style 0
Styles C and O-Measure p iston d i ameter ( 0 1 )
perpend i c u l a r t o p iston p i n a t 1 /2" above the
bottom of t h e s k i rt.
Figure 1 1 -4 . Measuring P iston Diameter.
A
2 . Use an inside micrometer, telescoping gauge ,
or bore gauge and measure the cylinder bore .
Take the measurement approximately 2- 1 /2 "
below the top of the bore and perpendicular to
the piston pin .
3 . Piston-to-bore clearance i s the difference be­
tween the bore and the piston diameter (step
2 minus step 1 ) . For style A pistons only,
clearance should be :
. 007" / . 0 1 0" for K1 6 1 -K34 1 . For piston styles C
and 0 , clearance should be :
K1 8 1 ,
. 0045" 1 . 0062"
for K32 1 , and . 0030" 1 . 0050"
VALVES
I nspection and Service
Carefully inspect valve mechanism parts . Inspect
valve springs and related hardware for excessive
wear or distortion . Valve spring free height should
be at approximately the dimension g iven in the
chart below. Check valves and valve seat area or
inserts for evidence of deep pitting , cracks or dis­
tortion . Check clearance of valve stems i n guides.
See Figure 1 1 -5 for valve details and specifica­
tions.
. 0035" 1 . 006" for K9 1 ,
. 0034 " 1 . 0051 " for
for K30 1 ,
. 0050 " 1 . 0067"
for K34 1 .
1 1 . 3