Assuming that you have, or can get, a set of jumper cables when you find that your motorcycle battery is dead, getting the bike started is no big deal. But you can cause harm if you do it wrong.

Connecting batteries in series is what you do when you pop a couple of cells into your flashlight. That is, you put the positive terminal of one battery into contact with the negative terminal of another. The result is that the voltage provided is the sum of the voltages of both batteries. This is NOT THE WAY to connect motorcycle batteries!!!

When you connect batteries in parallel, by placing the positive terminal of one into contact with the positive terminal of the other and the same with the negative terminals, then the voltage that results remains the same, but the amount of current that can be produced is raised. You need current to power your starter.

Always be sure that the batteries you will be connecting together are of the same voltage.
Always connect the same polarity terminals together when jumping a battery.

Always wear eye protection when jumping a battery!

Make sure the vent tube on your battery is connected properly.
Make sure you are in a well ventilated environment - preferably outside.
Do NOT SMOKE while charging or jumping a battery.

Always start by making the connections on your dead battery.

(It might be better if you connected the negative lead to some part of your bike frame rather than to the negative battery terminal in order to keep any potential sparks away from generated hydrogen gas. However, there cannot be a spark from a dead battery, connecting the leads to the dead battery does not yet create a circuit, and in the next step you will take pains to avoid a spark with the live battery.)

Next, connect the positive (red) lead of the other end of the jumper cable to the functional battery's positive terminal. Again, wiggle the connection to encourage a good 'bite' of metal to metal. [If you are unable to gain access to the battery terminals on the donor vehicle, (many are very inconveniently located), you can connect the positive jumper lead to the starter solenoid lead closest to the battery.]

Finally, connect the remaining (black) lead to some part of the frame of the donor vehicle. Since the negative terminal of all modern vehicles have their negative battery terminal connected to the frame of the vehicle (called a 'ground'), this is the same as connecting to the negative terminal of the battery. However, since this last connection establishes a live circuit, it is possible for there to be a spark when the connection is made. You want any spark that might occur to be as far away from the battery as is reasonably possible.

Though MOST vehicles today use a negative ground, you must check to be sure that is the case before you connect the jumper cables to the donor battery. You can still use it even if that vehicle uses a positive ground, but you must remember to connect positive to positive and negative to negative.

If your battery is dead because it has developed an internal short, you can easily kill the donor battery when connecting it if the donor vehicle is not running at the time, but
If it is running and your battery is shorted you can damage the donor vehicle's voltage regulator system when you connect the jumper cables.

DO NOT START THE DONOR VEHICLE while it is connected to your motorcycle battery.

You do not have to be in a hurry while the jumper cables are connected. Indeed, so long as those cables are connected the donor battery is charging your motorcycle battery. After a couple of minutes the charge might be sufficient for you to be able to start your bike using just your own battery. In any event, it is now time to start your motorcycle. It is usually best to simply leave the jumper cable in place when you start the motorcycle.

Let your motorcycle run about 15 seconds while the jumper cable remains in place. Then, remove the negative (black) lead from the donor vehicle's frame (assuming it was a normal negative-ground system). Again, this step could cause a spark, but because the connection is away from the battery, it poses no danger.

Now disconnect the positive (red) lead from the donor battery terminal. You must be very careful not to let the jumper cable leads touch each other at this time. To do so WILL KILL YOUR MOTORCYCLE BATTERY, possibly permanently!

Disconnect the jumper leads from your motorcycle battery (in any order - there cannot be a spark from doing so.)

Let the motorcycle idle (high - over 1,000 RPM) for a few minutes before you attempt to ride off into the sunset to give its charging system a chance to restore your battery.

Thank the person who donated the use of their battery to get you going again. (You could have killed *HIS* battery if you had done it wrong, so he took some risk for you as well as provided his courtesy.)

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