The first function of engine flywheel is to store energy. When the engine is working, the flywheel stores energy and inertia so that the crankshaft can continue to rotate. Because the inertia of the flywheel rotation is large, it can reduce the fluctuations in engine speed and make the operation more stable. Without the cushioning effect of the flywheel, the speed of the engine will fluctuate significantly, and the power output will be incoherent. This makes the flywheel an indispensable component in a single-cylinder or multi-cylinder engine.