How to Jump Start a Motorcycle Battery From a Car
Manufacturers do not recommend attempting to jump start a motorcycle battery from a car. The reason is that car batteries are much larger and have a much higher amperage (more power) and can damage a motorcycle battery. Life doesn’t always cooperate, however, and you may find yourself with little alternative. The good news is that with proper precautions, you can jump start a motorcycle battery from a car without damaging the bike and with little risk to the battery.
Turn off both vehicles and make sure lights and other equipment is also turned off. Open the car hood and remove any protective caps over the battery terminals on both vehicles. Leave the car turned off until you are finished jump starting the motorcycle and have disconnected the jumper cables.
Connect one red clamp to the positive terminal of the motorcycle battery. Make sure the clamp does not touch any other metal part. Connect the black clamp to the motorcycle frame (try to choose a point free of paint or chrome to avoid scratches or discoloration). It’s better not to connect directly to the negative terminal as this increases the chance of damaging the battery.
Connect the other red clamp to the positive terminal of the car battery, making sure the clamp touches nothing else. Double-check that you are connecting positive to positive. Next, connect the black clamp to the negative terminal of the car battery, being careful not to touch the positive clamp in the process. Leave the car turned off.
Start the motorcycle. Unless the battery is totally gone, it should start right up. Let it run a few minutes to warm up the motorcycle engine before disconnecting the jumper cables.
Disconnect the jumper cables in the reverse of the order you connected them (Steps 2 and 3). Be careful to keep the clamps from touching anything metal until the cables are fully disconnected. Leave the motorcycle running until you drive it home or to a bike shop to get a new battery or a proper recharge.