How to fix motorcycle charging and electrical problems?

This is the most common problem as motorbike batteries are small due to space constraints and some manufacturers are also trying to reduce the overall weight of the motorcycle

Symptoms

You can hear the starter motor cranking, but it does not have enough power to start the engine. The sound gets weaker as the leftover juice from the battery gets drained and you hear the starter give up sooner and sooner at each attempt. When the battery is completely drained it won't make a sound.

How to know it's not a flat battery?

The starter motor keeps cranking constantly and powerfully (you cannot hear it dying off) as you are attempting to start the vehicle is a sign of a charged battery

How to fix it?

1. Kickstarting is most obvious and unlikely option as most bikes nowdays lack this lever
2. Pushstarting
3. On the roadside if you suspect a dying battery but you still heard it cranking almost good enough at the first time do not keep on trying as you drain it further. Unplug the headlights as they are the main source of power drain then try again
4. Try to jumpstart off another motorbike (best to always keep cables under the seat). You might need to rev the engine of the other motorcycle if it has a smaller battery, so the alternator will supply extra power (in case you attempt to jumpstart a 1000cc sports bike off a 125cc scooter)
5. Recharge the battery. A battery charger normally costs less than a new battery
6. You only need to buy a new battery if it does not hold the charge

Can I charge a car battery with a motorcycle charger?

Most car and motorcycle batteries are 12 volt, they just differ in capacity, so it can take 2-3 days to fully charge a car battery with a motorbike battery charger. For example it took 60 hours to fully charge a 48 Ah car battery deflated to 6.4 volts with an Optimate 3 motorcycle battery charger.

The alternator generates electricity and recharges the battery while the engine is running

Symptoms

The bike shows symptoms of a flat battery after longer journeys (10 miles+) or even dies off while riding. Check the voltage at the battery with a multimeter, it should increase while revving the engine.

How to know it's not the alternator?

After jumpstarting the motorcycle runs fine means it is supplying the ignition system with enough power. Attach a multimeter to the poles of the battery to check the voltage (should be between 12-12.6 volts with ignition off), then start the engine (should go up to around 13 volts) and rev it (now it should peak to over 14 volts).

How to fix it?

1. Further investigation required to determine the faulty part
2. Possible faulty stator (around £80), test the power output with a multimeter on all 3 leads
3. Possible faulty regulator/rectifier (around £60)

Symptoms

Starting the motorcycle blows the fuse immediately killing the electrical system to prevent further damage

How to fix it?

1. Ensure the correct amperage fuse is fitted
2. If keeps blowing it's a sign of a shorted circuit (an exposed wire touching e.g. the body)
3. Water in the electrical/wiring system (this is very rare)

Symptoms

The motorcycle starts fine in neutral, but when first gear is engaged the engine stalls immediately

How to know it's not the kickstand switch?

If the motorcycle fails in start in neutral or still runs after a gear is engaged

How to fix it?

1. Ensure the kickstand is folded up (as a safety feature in some models)
2. Possible dust built up as the kickstand switch cannot move freely, try moving it first to ensure this is the problem, if so clean or replace

Symptoms

The motorcycle does not start at all or only when the clutch is pull/released at a certain position

How to know it's not the clutch switch?

Unplug the connector under the clutch and create a direct electrical connection between the two contact points the try starting the vehicle

How to fix it?

1. Pull the clutch in completely (some bikes won't start without it as a safety feature)
2. Replace the faulty part

Symptoms

Intermittent starting problems or clicking sounds from the starter after the engine started

How to know it's not the starter relay?

Electrical testing of the starter relay with a multimeter is required

How to fix it?

1. Check the emergency kill switch (some use it as an OFF switch, which is incorrect: emergency is in the name, OFF is marked on the ignition, just turn the key left)
2. Ensure the battery is not completely flat
3. Test and replace the starter relay if needed