Onan DJA Series User Manual

ENGINE DISASSEMBLY
CYLINDER HEAD, VAIVES
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,
dean the combustion chamber 'and valve seats at regular
intervals.
VALVE CLEARANCE
Check valve clearance when the engine is at room temper-
ature (about 70
o
n.
1. Tum the flywheel until the cylinder is on its compres-
sion stroke. Use a socket wrench on the flywheel screw
hex head.
To determine ifthe cylinder is in its compression stroke,
observe the action of the push rods as the engine is
rotated in a clockwise direction. The exhaust valve
push rod will be in its lowest position and the intake
valve push rod will be moving downward. As the piston
reaches top dead center, the flywheel timing mark should
be aligned with the timing pointer and the valve push
rods stationary.
2. Now turn the flywheel clockwise for an additional 10
to 45-degrees. 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, ad-
just the locknut which secures the rocker arm to the
cylinder head (see Fig. 11-1). Loosen the locknut to
increase clearance and tighten it to reduce clearance.
4. After allowing engine to cool, check the clearance with
a feeler gauge between the rocker arm and the valve
(see Fig. 11-2). Increase or reduce the clearance until
the proper gap is established. Correct valve clearance
is .011" intake and .008" exhaust.
ADJUST VALVE
CLEARANCE HERE
VALVE
SPRING
RETAINER
VALVE
SPRING
OIL SEAL-
(INTAKE VALVE
ONLY)
f
LROCKER
"ARM
;
FIG. 11-1
ROCKER ARM
WRENCH
LOCK NUT
FEELER GAUG
A933
VALVE
FIG. 11-2
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 compres-
sion gage 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.
30

Onan DJA Series Specifications

General

Brand	Onan
Model	DJA Series
Category	Engine
Language	English