If a lawnmower engine vibrates excessively while running, what could be the likely cause?

When a lawnmower engine vibrates excessively while running, a bent crankshaft or blade is often the likely cause. The crankshaft, which converts the linear motion of the pistons into the rotational motion necessary to drive the mower blades, must be perfectly straight for smooth operation. A bend can lead to an imbalance, causing the engine to vibrate as it operates.

Similarly, if the blade itself is bent, it disrupts the uniform cutting action and can create uneven weight distribution, resulting in vibrations. This type of mechanical failure directly affects the way the mower functions and can lead to further engine damage if not addressed.

While improper fuel mixture, faulty spark plugs, and low oil levels can cause a range of other issues in an engine, such as poor performance, stalling, or noise, they do not directly contribute to excessive vibrations in the same way that a bent crankshaft or blade does.