The most common cause of "the motorcycle won't start" complaints is a flat or tired battery. Motorcycle batteries are much smaller than car batteries; on a motorcycle left unused for a long time, or with equipment that draws constant current such as an alarm or tracker, they can run flat within a few weeks. A little knowledge and a simple charger remove most of this problem.
1. Battery types
| Type | Characteristics | Maintenance |
|---|---|---|
| Conventional (wet, lead-acid) | On older and cheaper motorcycles. Has cell caps. | Fluid level is checked and distilled water added if necessary. Watch for acid leaks. |
| AGM (maintenance-free) | The most common type today. Sealed, no fluid added. | Only the state of charge is monitored. The caps are not opened. |
| Gel | Resistant to vibration, sealed. | Needs a suitable charging programme; must not be charged at high voltage. |
| Lithium (usually LiFePO4) | Very light, long-lived, expensive. | A lithium-compatible charger is essential. The "desulphation" or high-voltage modes of lead-acid chargers can damage a lithium battery. |
When replacing a battery, use the type, capacity and size in the motorcycle's owner's manual. Before switching to a lithium battery, make sure the motorcycle's charging system is compatible.
2. Understanding the battery's condition
Measuring the battery with a simple multimeter takes a few seconds. Take the measurement with the engine off, after the engine has not been run for at least a few hours.
- Rough values for a lead-acid / AGM battery: 12.6 V and above is generally regarded as full, around 12.4 V half full and 12.0 V and below as empty. A lead-acid battery left empty for a long time can suffer permanent damage.
- For lithium batteries the resting voltage is different; see the manufacturer's values.
- With the engine running: If the voltage rises above the resting value when the revs go up a little, the charging system is working. If the value is below or well above the range in the manual, there may be a fault in the alternator or the regulator-rectifier.
Signs of a weak battery
- The starter turns slowly and reluctantly, there is a clicking sound
- The dashboard lights go out or flicker when you press the starter
- It is harder to start on cold mornings
- The battery is swollen, cracked or the terminals are oxidised white/green
3. Trickle charger (smart charger)
It is one of the most useful small investments for a motorcyclist. The difference from an ordinary charger is that it cuts the charge when the battery is full and switches to maintenance (protection) mode only.
- It can stay connected for weeks in winter or on a motorcycle that is not used for a long time.
- With most units comes a socket lead that attaches permanently to the battery; it is brought out from under the seat so the battery doesn't have to be removed every time.
- Choose a low-current unit suitable for motorcycle batteries. High-current chargers made for car batteries can heat a small battery and shorten its life.
- If you have a lithium battery, make sure the unit has a lithium mode.
- Charge in a well-ventilated place; lead-acid batteries can give off flammable gas while charging.
4. Winter storage
- Fully charge the battery.
- If it is to stay in the motorcycle, connect it to a trickle charger.
- If you have no trickle charger, remove the battery and store it in a cool, dry place, checking the voltage and charging it every few weeks.
- When removing, take off the negative (-) terminal first, then the positive (+). When fitting, positive (+) first, then negative (-).
For the rest of the winter preparation see the winter guide.
5. Jump-starting: the safe order
Connection order
- Make sure the ignition of both vehicles is off.
- Connect the red lead to the positive (+) terminal of the flat battery.
- Connect the other end of the red lead to the positive (+) terminal of the good battery.
- Connect the black lead to the negative (-) terminal of the good battery.
- Connect the other end of the black lead not to the flat battery but to an unpainted metal earthing point (the frame, a bolt on the engine block) of the engine to be started. If access is difficult and the manual allows it, it can be connected to the negative terminal.
- Start the engine. If it doesn't start after a few tries, don't hold the starter for long; the starter motor heats up. Wait a little and try again.
Disconnection order (the exact reverse of connection)
- Remove the black lead from the earthing point.
- Remove the black lead from the good battery.
- Remove the red lead from the good battery.
- Remove the red lead from the battery of the engine that has started.
Jump-starting from a car
When jump-starting from a car battery, don't run the car's engine. The charging system of a running car can strain the motorcycle's small electrical system. A switched-off car battery is generally enough to start a motorcycle. Even so, if there is a specific warning about jump-starting in your motorcycle's manual, follow it.
Portable jump starter
Power bank type lithium jump starters are a great convenience on a long trip. Most have reverse-connection protection. Choose one with power suitable for a motorcycle and charge the unit regularly too.
6. After it starts
- Don't switch off a jump-started engine after a short idle; the battery doesn't charge that way. If possible, ride for a while, then fully charge the battery with the charger.
- If the battery goes flat again in a short time, the cause may be the battery itself, the charging system or equipment drawing constant current. Have the service centre measure the parasitic drain and charging voltage.
If the motorcycle won't start, check beyond the battery
- Side stand sensor: With the motorcycle in gear and the side stand down, most won't start.
- Is the engine kill switch in the "run" position?
- Are you in neutral (N), or is the clutch pulled in?
- Is there fuel, has a fuse blown?
- Is the immobiliser chip in the key being recognised (dashboard warning)?