It is possible to jump-start a motorcycle using a car battery. However, the procedure is different than the procedure for jump-starting a car. For example, the car's engine should not be started when jump-starting a motorcycle with a car.
A car battery delivers 12 volts of power when the engine is idle, which is sufficient to start a motorcycle without damaging the motorcycle's battery. The battery delivers much more power when the engine is running, and the extra power is harmful to the motorcycle's battery. If no car is available, a dead motorcycle can sometimes be push-started in second gear.