3.2
Section 3
Troubleshooting
Engine Knocks
1. Excessive engine load.
2. Low crankcase oil level.
3. Old or improper fuel.
4. Internal wear or damage.
Engine Loses Power
1. Low crankcase oil level.
2. High crankcase oil level.
3. Dirty air cleaner element.
4. Dirt or water in the fuel system.
5. Excessive engine load.
6. Engine overheated.
7. Faulty spark plug.
8. Low compression.
9. Exhaust restriction.
Engine Uses Excessive Amount Of Oil
1. Incorrect oil viscosity/type.
2. Crankcase overfilled.
3. Clogged or improperly assembled breather.
4. Worn or broken piston rings.
5. Worn cylinder bore.
6. Worn valve stems or valve guides.
External Engine Inspection
Before cleaning or disassembling the engine, make a
thorough inspection of its external appearance and
condition. This inspection can give clues to what
might be found inside the engine (and the cause)
when it is disassembled.
• Check for buildup of dirt and debris on the
crankcase, cooling fins, grass screen and other
external surfaces. Dirt or debris on these areas are
causes of overheating.
• Check for obvious fuel and oil leaks, and
damaged components. Excessive oil leakage can
indicate a clogged or improperly assembled
breather, worn or damaged seals and gaskets, or
loose or improperly torqued fasteners.
• Check the air cleaner cover and base for damage
or indications of improper fit and seal.
• Check the air cleaner element. Look for holes,
tears, cracked or damaged sealing surfaces, or
other damage that could allow unfiltered air into
the engine. Also note if the element is dirty or
clogged. These could indicate that the engine has
been underserviced.
• Check the carburetor throat for dirt. Dirt in the
throat is further indication that the air cleaner is
not functioning properly.
• Check that the oil level is within the operating
range on the dipstick, or if it is low or overfilled.
• Check the condition of the oil. Drain the oil into a
container - the oil should flow freely. Check for
metal chips and other foreign particles.
Sludge is a natural by-product of combustion; a
small accumulation is normal. Excessive sludge
formation could indicate the oil has not been
changed at the recommended intervals, the
incorrect type or weight of oil was used, overrich
carburetion, and weak ignition, to name a few.
Cleaning the Engine
After 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.
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