Onan DJA Series User Manual

2. Oil the stem of each valve lightly and insert each
in its own guide.
3. Check each valve for a tight seat with an air
pressure type tester. If a tester is not available,
make pencil marks at intervals on the valve face
and observe if the marks rub off uniformly when
the valve is rotated part of a turn in the seat. If
the seat is not tight, regrind the valves.
4. Using a valve spring compressor, compress each
valve spring and insert the valve spring retainer,
and retainer locks.
5. Install the head assembly and gasket to the cylin-
der block. Tighten the head bolts in a "clockwise"
manner starting with 12 o'clock and follow in the
order shown around the "clockface" (Figure 40),
finishing at the 10 o'clock position. Torque the
bolts evenly to 44-46foot-pounds.
FIGURE 40. TIGHTENING HEAD BOLTS
INTERNAL DISASSEMBLY
If engine disassembly is necessary, observe the fol-
lowing order (i.e. Flywheel, Gear Cover...). As dis-
assembly progresses, the order may be changed
somewhat as will be self-evident. The engine
assembly procedure is the reverse of disassembly. Any
special assembly instructions for a particular group
are included in the applicable section. When reassem-
bling, check each section for these special assembly
instructions or procedures.
FLYWHEEL
Remove the blower housing. The flywheel is a tapered
fit on the crankshaft. Improvise a puller using at least
a 7./16-inch bar and drilling two 7/16-inch holes 2-7/8-
inches between centers. Loosen the flywheel mounting
screw a few turns. Place bar against the flywheel
screw, attach bar using two 3/8-16 thread screws in
the holes provided in flywheel. Alternately tighten the
screws until flywheel is free.
Replacement flywheels are supplied without the timing
markings because each flywheel must be fitted to its
engine. The only accurate method of determining the top
dead center (TDC) and port closing points is.to measure
the piston travel. This is a critical measurement and
should be attempted only with accurate, dependable
equipment.
With the flywheel mounted, remove the head and install
a depth gauge over the front piston. Rotate the flywheel
to find the TDC position on the compression stroke and
mark this point on the flywheel. Next, turn the flywheel
counterclockwise until the piston drops exactly 0.102-
inch from TDC. This is the port closing point, 17°
BTDC. Mark it on the flywheel.
6. Install the exhaust manifold, nozzles, glow plugs
and oil lines.
7. Install the valve stem caps.
8. Install the push rods, rocker arms and rocker arm
nuts.
9. Set the valve clearance. See Figure 38.
10. Install and adjust the decompression mechanism.
11. Install the rocker cover. Remove the solenoid, dip
plunger "O" ring in oil and reinstall when cover
is on engine.
IMPORTANT: Alter the first SOhours ol operation,
retighten the cylinder head bolts and check valve
clearance.
Ring Gear: To remove the ring gear (if damaged), saw
part way through, then break it using a cold chisel
and heavy hammer.
To install a new ring gear, place it in an oven heated
to 380 - 400
0
F for 30 to 40minutes.
j^CAUTION
Do not heat with a torch.
When heated properly, the ring will fall into place on
the flywheel. If it does not go on all the way by itself,
drive it into place with a hammer. Do it fast and do not
damage the gear teeth. The ring will contract rapidly
and may shrink to the flywheel before it is in place.
If this occurs, a new ring gear may be required.
37

Onan DJA Series Specifications

General

Brand	Onan
Model	DJA Series
Category	Engine
Language	English