Onan NHC Series Operator's/Service Manual And Parts Catalog page 123

The standard cylinder bore size appears i n Dimensions.
and Clearances. '
OIL PUMP
To remove the o i l pump, i t is necessary to detach the
intake cup assembly as shown i n Figure 58.
Check the o i l pump thoroughly for worn parts. O i l
the pump to prime i t before r e i n s t a l l i n g . Except for
gaskets, the component parts of the pump are not.
available individually. The suction cup is available
separately. I n s t a l l a new pump assembly, i f required.'
O I L PUMP I N T A K E C U P
C R A N K C A S E T U R N E D jj
ON L E F T S I D E - *
UNSCREW OIL PUMP A S S E M B L Y ^
FROM I N T A K E CUP A T THIS P O I N T
To reassemble reverse the procedure.
O I L PUMP A S S E M B L Y - ^
F I G U R E 58. OIL PUMP ASSEMBLY
CYLINDER HEADS
Remove the cylinder heads for cleaning at least every
400hours or when poor engine performance is noticed.
1. Use a 1/2 inch socket wrench to remove cylinder
. head bolts. L i f t heads off.
' > ^ ^ ^ v ^ D o not remove heads when they
^ y ^ ^ ^ v ^ s ^ i are hot. Warpage may occur.
2. After removing heads, clean out a l l carbon de-
posits. Be careful not to damage the outer sealing
edges where gaskets f i t . The heads are made of
aluminum and can be damaged by careless handling.
3. Use new head gaskets and clean both the heads
and. the cylinder block thoroughly where the head
gaskets rest.
4. Place heads in position and follow head torque
- tightening sequence shown in Figure 59".'- Start out
tightening a l l bolts to 5 ft-lb, then 10 f t - l b , etc.,
until a l l bolts are torqued to 17-19 f t - l b .
5. Recheck torque befbre engine.. has run a total
of 50 hours. ,
%i j y
L E F T C Y L I N D E R
R I G H T C Y L I N D E R
F I G U R E 59. HEAD BOLT TIGHTENING S E Q U E N C E
38