But usually the problem is a worn or stretched chain or worn or bent sprockets. In these cases, replace the chain, the sprockets, or both before riding again. When the chain breaks, you'll notice an instant loss of power to the rear wheel. Close the throttle, and brake to a stop. Chain slippage or breakage can be avoided by proper maintenance.
Engines seize when they are low on oil.
Without oil, the engine's moving parts can't move smoothly against each other, and the engine overheats. The first sign that an engine needs oil may be a loss of engine power. You may also notice a change in the engine's sound. If available, check the engine oil pressure light and temperature gauge. If you ignore these warnings and don't add oil, the engine may seize.