3.3
Section 3
Troubleshooting
3
Basic Engine Tests
Crankcase Vacuum Test
A partial vacuum should be present in the crankcase
when the engine is operating. Pressure in the crankcase
(normally caused by a clogged or improperly
assembled breather) can cause oil to be forced out at
oil seals, gaskets, or other available spots.
Crankcase vacuum is best measured with either a
water manometer or a vacuum gauge (see Section 2).
Complete instructions are provided in the kits.
To test the crankcase vacuum with the manometer:
1. Insert the stopper/hose into the oil fi ll hole. Leave
the other tube of manometer open to atmosphere.
Make sure the shut-off clamp is closed.
2. Start the engine and run at no-load high speed
(3400-3600 RPM).
No Crankcase Vacuum/Pressure in Crankcase
Possible Cause Solution
Crankcase breather clogged or inoperative. Replace valve cover and recheck pressure. Breather
is integral part of valve cover and cannot be serviced
separately.
Seals and/or gaskets leaking. Loose or
improperly torqued fasteners.
Replace all worn or damaged seals and gaskets. Make sure
all fasteners are tightened securely. Use appropriate torque
values and sequences when necessary.
Piston blow by or leaky valves (confi rm by
compression or cylinder leakdown tests and
inspecting components).
Recondition piston, rings, cylinder bore, valves, and valve
guides.
Restricted exhaust. Check exhaust screen/spark arrestor. Clean or replace as
needed. Repair or replace any other damaged/restricted
muffl er or exhaust system parts.
Cleaning the Engine
A er inspecting the external condition of the engine,
clean the engine thoroughly before disassembling
it. Also clean individual components as the engine
is disassembled. Only clean parts can be accurately
inspected and gauged for wear or damage. There
are many commercially available cleaners that
will quickly remove grease, oil, and grime from
engine parts. When such a cleaner is used, follow
the manufacturer’s instructions and safety precautions
carefully.
Make sure all traces of the cleaner are removed before
the engine is reassembled and placed into operation.
Even small amounts of these cleaners can quickly
break down the lubricating properties of engine oil.
3. Open the clamp and note the water level in the
tube.
The level in the engine side should be a
minimum of 10.16 cm (4.00 in.) above the level in
the open side.
If the level in the engine side is less than specifi ed
(low/no vacuum), or the level in the engine side
is lower than the level in the open side (pressure),
check for the conditions in the table below.
4. Close the shut-off clamp before stopping the
engine.
To test the crankcase vacuum with the Vacuum/
Pressure Gauge Kit (see Section 2):
1. Remove the dipstick or oil fi ll plug/cap.
2. Install the adapter into the oil fi ll/dipstick tube
opening.
3. Push the barbed fi ing on the gauge solidly into
the hole in the adapter.
4. Start the engine and bring it up to operating
speed (3400-3600 RPM or application specifi c).
5. Check the reading on the gauge. If the reading
is to the le of "0" on the gauge, vacuum or
negative pressure is indicated. If the reading is to
the right of "0" on the gauge, positive pressure is
present.
Crankcase vacuum should be a minimum of
4 inches of water. If the reading is below the
specifi cation, or if pressure is present, check the
table below for possible causes and remedies.
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