First: The carburetor is improperly adjusted. Combustible mixture is too dense, can not be fully burned, residual combustible mixture into the exhaust pipe, resulting in shooting.
Second: spark plugs intermittent ignition. When the spark plugs are in bad or broken fire, the combustible mixture with no ignition and combustion enters the exhaust pipe, and the high temperature and high pressure exhaust gas discharged from the next combustion work cycle is ignited by fire.
Third: ignition coil failure. Ignition coil damp or leakage, in fact, is a circuit fault, even if the CDI, high-pressure package and spark plugs are normal, will also cause ignition instability or broken fire, resulting in firecrackers.
IV: The distribution of gas in the time of failure (relative to the four-punch engine). Four-punch engine valve clearance is not strict, valve ablation closed, valve phase overlap angle is too large, timing gear installation does not cause exhaust door opening early, resulting in the phenomenon of cannon.
Five: The ignition time is too late. In the case of incomplete combustion of the combustible mixture in the cylinder, the vent has been opened, causing the unburned combustible mixture to continue to burn in the exhaust pipe, causing the fire to blow.