How to Diagnose Faults of Two-Stroke Engine and Four-Stroke?
Engine lack of enough power, hard to start, fuel consumption increase, and all components cannot work properly are the main faults. The voice has reflected on each engine components and parts abnormal working conditions.
RC model airplane engine lack of power, difficult to start and fuel consumption increase are the same common point for two-stroke engine and four-stroke engine, except for the ignition system, carburetor system, transmission system, piston, piston ring and cylinder wear, the main causes lead to the above faults are decided by the different of the two engines' valve mechanism and gas mixture.
Four-stroke engine fault diagnosis:
a) Improper adjustment of the valve timing;
b) Improper adjustment of the valve clearance, too big or too small;
c) The cam wear;
d) The valve ablation, and valve rod get bending, valve spring force weaken so that makes the valve leakage;
e) The wear get bad between the two axles axle necks and axle hole, due to the gap between the shaft and hole increase, the camshaft produced some displacement during it is rotating, and that has made the valve opening a small space.
Two-stroke engine fault diagnosis:
a) The crankshaft oil seal leakage;
b) The air intake closed lax;
c) Two-stroke engine mixture containing oil, combustion chamber, scavenging port, exhaust port and exhaust pipe, it is easy to form carbon deposit, that will block the air flow and then make the engine to get into a high temperature.
d) Oil has taken a large proportion in the engine mixture.
The diagnosis of four-stroke engine noise:
Four-stroke engine crankshafts, cylinder, piston assembly are all working under good lubrication condition, and it is rarely to appear noise. While the valve mechanism is working under a bad condition, so the noise is mainly coming from the valve mechanism.
a) The improper adjustment of the timing chain, too loose or too tight are all not allowed. If the timing chain was stretched to its limited, then you cannot adjust it. Or driving and driven timing gear was serious wear and the tensioning device was damaged.
b) Two axle neck of the camshaft and axle hole wear worse;
c) The valve clearance is too large;
d) The valve rod bending, and valve spring was broken;
e) Rocker arm shaft and radial hole wear badly;
The diagnosis of two-stroke engine noise:
Two-stroke engine crankshaft connecting rod assembly, cylinder, and piston assembly are all under bad lubrication condition, and it will release different levels of noise depending on the amount of wear.
a) The crankshaft bearing wear;
b) Wear to the big and small needle roller bearing of connecting rod, axis and hold
c) The piston, piston ring and cylinder wear;
d) Combustor has serious carbon deposits, which made the compression ratio increases and appear the deflagration sound.
e) The fault of the oil pump which causes the mixture does not apply for the oil and appear the noise.
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