Battery
First lets start out by saying if you plan to do any work to your bike other than the inspections, you have to disconnect the battery cables so you don’t accidentally start the bike. Always disconnect the negative cable first. The negative cable is grounded to the frame, so if you accidentally touch the frame or any metal nothing bad will happen. If you disconnect the positive side first and accidentally touch the frame or metal you are creating a ground which will let the juice run right through you, maybe start a fire, just not good any way you look at it. To disconnect the negative cable on the battery you’ll need that all important 10mm wrench. Make sure when you disconnect the positive cable it won’t be able to touch anything metal, like the frame. I usually stick a shop rag or a short piece of rubber hose around the terminal to be sure of no contact. If you maintain your battery properly from the beginning you should be able to get 3-5 years out of it. Lets talk about inspecting the battery. First the battery contains electrolyte which is a sulfuric acid solution that can do some damage to your skin and eyes. One of my lucky jobs here at the shop is filling and charging batteries. I’ve had the acid spill on my clothes and have lost many a good pair of jeans to battery acid. Trust me you don’t want this stuff on you, so please wear eye protection and gloves when handling the battery. Most of the newer bikes come with a sealed battery making it impossible for the acid to spill out but nonetheless you should always be cautious. When installing a new battery it must be charged fully to insure a long life. Follow the instructions that come with the new battery on how to charge it initially. The newer sealed type batteries have different charging instructions than the earlier wet cell types. If you fill your battery and just give it a quick charge because you’re in too much of a hurry to ride, the second you hit the start button and put a load on the battery you just guaranteed yourself a short battery life. If the battery wasn’t charged correctly initially it will never be able to be charged fully. So like anything in life, slow down take your time and do it right.

Inspecting the battery and charging system
The top of the battery should be clean from dirt and residue. If the cables and terminals have any oxidation or corrosion you will need to clean them with a wire brush or a piece of sandpaper. Check all the fasteners for tightness and any breakage. Look at the battery posts to make sure they haven’t been warped from overheating. Basically look the whole battery over for cracks or warps etc. If your bike won’t start and it seems the battery is dead this is when having a volt meter comes in handy as this is what you’ll use to test the voltage of the battery. More often than not you’ll find that checking the cables for loose terminals, corrosion, frayed ends or worn insulation leading to a short is more than likely the culprit of the dead battery. If you don’t have a volt meter, call your local shop to get your bike in for an appointment and have the shop do a voltage test for you. A great safe and easy way to maintain the life of your battery is with a battery tender. This will charge the battery for you and keep your battery fully charged, prolonging the life of your battery. When you hook the battery charger to the battery, red is for positive and black is for negative. Your tender will tell you when the battery is fully charged. I recommend you take the battery off the bike to charge it, if the battery would happen to overcharge it can overflow and the acid would do things to your bike that won’t be pretty or safe to parts on your bike. If you’re using a motorcycle Battery Tender you won’t have to worry about overcharging. The battery Tender will shut off automatically. Make sure the charger is turned off before you hook the battery up to it. Same thing when disconnecting, Have the charger turned off before removing the connectors. If you do take the battery out of the bike the positive gets disconnected last when removing, and connected first when re-installing. Make sure you refer to your service manual before attempting battery removal. NOTE. Always disconnect the negative cable first when removing, and connect the negative cable last when re-installing.

Charging system.
I want to explain a little about the motorcycle charging system. Basically there are two charging system set up’s on American v-twin bikes. The early style charging systems consists of the battery, generator and a regulator. The generator creates a direct current (DC). The regulator will maintain the voltage to the battery and all other units such as lights, Ignition etc. at a constant voltage unaffected by engine speed or load. Now if for some reason you find yourself getting into to the charging system on a generator type bike and disconnect the battery then the generator is going to need to be polarized before starting the engine. If you don’t polarize the generator first, the charging system will work in the opposite manner and actually drain the battery voltage instead of maintaining or “regulating” it. Please refer to your service manual if you find yourself in need of charging system care and polarizing. On later style bikes usually 1978 and up the charging systems consists of the battery, voltage regulator and alternator (stator and rotor). The alternator is made up of the rotor, which is mounted on the engine sprocket shaft, and the stator you’ll find bolted to the crankcase. The rotor which contains magnets spins with the engine around the solidly mounted stator. The stator is a group of copper wound coils. The rotor spinning around the stator creates an alternating (AC) current of approximately 30 to 50 volts. This current flows to a voltage rectifier/regulator. The regulator converts the AC current to the DC direct current that your battery requires. This unit also limits (regulates) the output it sends. If the charging system on your bike is causing problems the first place to start is at the battery. Again you’re checking those battery terminals and cables for corrosion or bad connections. If you see nothing visibly wrong you’ll want to next inspect and test the charging system components. Refer to your service manual for all correct procedures if you want to perform the tasks yourself. A very common problem with charging systems is the voltage regulator wire pulling out away from the stator plug. Take two seconds to check that the voltage regulator plug is fully inserted in the stator plug. (Located on the forward side of your primary cover)You can purchase voltage regulator retaining clips to keep that plug from backing out. Nature of the beast, vibration will shake things loose on a motorcycle.
I mentioned the ignition coil being responsible for sending the voltage to the spark plug. Let me talk a little more about the coil. The coil is basically a transformer. It transforms the 12 volts from the battery into higher voltage to send to the spark plugs. Inside The coil there are 2 “coils” or windings a primary and secondary with a laminated iron core. This is all sealed in a water tight insulating compound. If tests show the coil is bad it is not something you can rebuild or repair, you must replace it. Your service manual will go into detailed explanations on how the ignition systems work on V-twin engines. Please refer to that section of the service manual for more in depth information.