Onan DJA Series User Manual

ENGINE DISASSEMBLY
CYLINDER HEAD, VALVES
The cylinder head assembly has alloy hardened faced
valves, release type rotators, alloy hardened inserts,
guides, rocker arms, injection nozzle and glow plug.
The push rods run through shields.
Maintenance:
Check the valve clearances at regular intervals. In
addition, clean the combustion chamber and valve seats
at regular intervals.
Valve Clearance:
Check valve clearance when the engine is at room tem-
perature (about 70
0
F).
1. Turn the flywheel until the cylinder is on its com-
pression stroke. Use a socket wrench on the fly-
wheel screw hex head.
i
To determine if the cylinder is in its compression
stroke, observe the action pf the push rods as the
engine is rotated in a clockwise direction. The
exhaust valve push rod will be. in its lowest posi-
tion and the intake valve push rod will be moving
downward. As the piston reaches rod dead center,
the flywheel timing mark should be aligned with
the timing pointer and the valve push rods sta-
tionary.
2. Now turn the flywheel clockwise for an additional
. 10 to 45degrees. There is no timing mark for this
position so it must be estimated. With the piston
located in this position, it will be in its power
stroke with both valves completely closed.
3. Cylinder head bolt torques should be 44 to 46 foot-
pounds. To change the setting of valve clearance,
adjust the locknut which secures the rocker arm
to the cylinder head (see Figure 37). Loosen the
locknut to increase clearance and tighten it to
reduce clearance. .
u
v
4. After allowing engine to cool, check the clearance
with a feeler; gauge between the rocker arm and the
valye (see Figure 38).^Increase or reduce the
clearance until the proper gap is established.
Correct valve clearance is 0.011-inch intake and
0.008-inch exhaust. ,
ADJUST VALVE
CLEARANCE HERE
VALVE
SPRING
RETAINER
VALVE
SPRING
OIL SEAL-
(INTAKE VALVE
ONLY)
/
.ROCKER
ARM
FIGURE 37. SETTING VALVE CLEARANCE
ROCKER ARM
WRENCH
LOCK NUT
FEELER GAUG
A933
VALVE
FIGURE 38. CHECKING VALVE CLEARANCE
.Testing: ,, .
The cylinder compression test can be used to determine
the. condition of valves, the piston, piston rings and
cylinder.
To check compression, run the engine until thoroughly
warm. Stop it, and remove the injection nozzle. Insert
the compression gauge in the injection nozzle hole,
crank the engine, and' note the reading. To check for
piston blow-by, squirt a small amount of SAE 50 oil
into the cylinder and repeat the check. An increase in
compression with oil in the cylinder indicates piston
blow-by.
35

Onan DJA Series Specifications

General

Brand	Onan
Model	DJA Series
Category	Engine
Language	English