What Causes Motorcycle Backfiring?

[DeAngelo]

Regarding the causes of motorcycle exhaust backfiring, the reasons are as follows: 1. Overly rich air-fuel mixture. An excessively rich combustible mixture causes backfiring in the exhaust pipe. At low engine speeds, the sound is heavy and unstable; at high engine speeds, the backfiring significantly improves or even disappears, which is a hallmark of backfiring caused by an overly rich mixture. 2. Excessive fuel level in the float chamber. This not only leads to an overly rich combustible mixture but also causes some fuel to enter the cylinder without sufficient atomization. The unburned fuel then exits into the muffler with the exhaust gases, where it reignites, resulting in backfiring. 3. Excessively small ignition advance angle. In four-stroke engines, incorrect valve clearance, burnt valves failing to close tightly, excessive valve overlap angle, or incorrect timing gear installation causing premature opening of the exhaust valve can all lead to backfiring.