Huansong UTV 700 2009, Service Manual

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GENERAL INFORMATION
1-47
Detonation
Detonation is the violent explosion of fuel in the combustion chamber before the proper time of
ignition. Using low octane gasoline is a common cause of detonation.
Even when using a high octane gasoline, detonation can still occur. Other causes are
over-advanced ignition timing, lean air/fuel mixture at or near full throttle, inadequate engine cooling,
or the excessive accumulation of carbon deposits in the combustion chamber.
Continued detonation can result in engine damage.
Power Loss
Refer to Poor Engine Performance in this chapter.
Engine Noises
Unusual noises are often the first indication of a developing problem. Investigate any new noises
as soon as possible. Something that may be a minor problem, if corrected, could prevent the
possibility of more extensive damage.
Use a mechanic’s stethoscope or a small section of hose held near your ear (not directly on your
ear) with the other end close to the source of the noise to isolate the location. Determining the exact
cause of a noise can be difficult. If this is the case, consult with a professional mechanic to determine
the cause. Do not disassemble major components until all other possibilities have been eliminated.
Consider the following when troubleshooting engine noises:
1. Knocking or pinging during acceleration can be caused by using a lower octane fuel than
recommended. May also be caused by poor fuel. Pinging can also be caused by an incorrect
spark plug heat range or carbon buildup in the combustion chamber.
2. Slapping or rattling noises at low speed or during acceleration—May be caused by excessive
piston-to-cylinder wall clearance (piston slap).
NOTE
Piston slap is easier to detect when the engine is
cold and before the piston has expanded. Once
the engine has warmed up, piston expansion
reduces piston-to-cylinder clearance.
3. Knocking or rapping while decelerating—Usually caused by excessive rod bearing clearance.
4. Persistent knocking and vibration occurring every crankshaft rotation—Usually caused by
worn rod or main bearing(s). Can also be caused by broken piston rings or a damaged piston
pin.
5. Rapid on-off squeal—Compression leak around cylinder head gasket or spark plug(s).
6. Valve train noise—Check for the following: