Yes, it is completely possible to jump-start a motorcycle with a car battery, but it’s not exactly the same process as you’d use for a car-to-car jump. Since car batteries are much bigger and more powerful than motorcycle batteries, it’s necessary to jump it from a car that is switched off rather than running. If the car is running the power could be too great for your motorcycle’s battery and electrics to jump properly. It won’t fry your battery, but it won’t do it any favors. Always ensure that the car is not running, and it should be no problem. If in doubt, a push start is an excellent plan B.