8 Signs A Motorcycle Has A Bad Ground (Explained)

Modern motorcycles use electricity generated by a battery to power many systems on the bike, but if the battery isn’t grounded properly, you can have operational issues. 

The electricity generated by the battery feeds power to the electric starting and ignition systems, lights, led screens, accessories, and sensors. 

Because any malfunction in the systems we’ve just mentioned can be bad for the operation of your bike, a grounding system is employed by the motorcycle to shed any excess voltage to avoid adding charge to the metal parts.

We’ve compiled a list of 8 signs that a motorcycle has a bad ground and offered some troubleshooting tips.

Hopefully, we can give you the information you need to help diagnose and fix any problems you may be having from a bad ground!

Here’s the short answer to signs your motorcycle has a bad ground:

If your motorcycle is having hard starts, simply not starting, flickering or dim lights, malfunctioning LED screens or accessories, you may have some issues with the grounding on your bike. Alternately, a battery that won’t keep a charge, a busted ignition coil, or any visible damage to the electrical wiring can each be a symptom of a bad ground.

How Does Grounding Work?

Ground wires are a common feature on all closed system batteries manufactured after 1971. If you have a battery made before 1971, your problems are way bigger than a faulty ground wire!

Creating an extra pathway for excess and potentially dangerous electrical current is called grounding because buildings shed this into the ground via a rod driven deep into the Earth.

It would be impossible to use a common ground like this for a non-stationary electrical system like the one on a motorcycle, so a motorcycle uses a ‘floating ground.’

Your bike’s floating ground is essentially the same thing as an earth ground, but instead of dispersing the excess electricity into the ground via a rod, it feeds it back into the negative side of a battery system.

Floating ground systems aren’t considered a true ‘earth ground’ but are equally useful for your bike’s electrical function.

1. Did You Just Get Shocked?

A bad ground won’t allow the excess voltage to be dispersed back into the negative side of your battery, so it can electrify pretty much anything metal on your bike. 

Fortunately, 9- and 12-volt batteries aren’t going to burn your bones from the inside, but one shock from your bike frame is enough to run around, wringing the shocked hand in the air, screaming curses in the air that would make a sailor blush.

Because electrical systems are designed to carry a certain amount of load through a very specific pathway, an ungrounded system can not only cause voltage leaks, but can electrify your chassis or components with enough power to cause malfunctions.

These can occur in both the systems that are losing voltage and anything that is gaining electrical load that it isn’t designed for.

To avoid electrical shock (or future shocking), turn off your bike. Once your bike is off, gain access to the battery and remove the battery wire from the negative terminal.

Make sure to tuck this negative battery wire or bend it safely away from the bike to reduce the risk of charging your bike system again.

2. Dim Or Flickering Lights

If you notice that your motorcycle’s lights have been dimming or flickering, it could be an issue with the grounding. 

If your lights are dimming, it is because enough electrical voltage isn’t reaching the intended light.

This means that the current will power the light, but won’t be strong enough to get the brightness that you need to safely operate your bike, especially in the dark.

Flickering lights can be a sign that you are getting too much voltage to the lights. Because electricity travels in pulses, the flickering is indicating that every few pulses, the light is receiving too much electrical current.

Oftentimes, this is because a faulty ground wire isn’t taking on the excess load of electricity.

3. Electrical Features Don’t Work All the Time

Just like the grounding problem we just covered in the section on dimming and flickering lights, too much or too little electrical voltage can negatively affect the function of other electrical features of your bike.

Do you have a malfunctioning LED screen, hand warmers, accessory lights, or radio?

There’s a good chance that your faulty ground is causing short outages that keep a consistent current running to any of these electricity-powered features.

It can be an especially good indicator of faulty grounding if these problems are inconsistent, changing, or turning on and off as if by random coincidence. 

4. Fuel Pump Is not Functioning Properly

If you have grounding issues, it could negatively affect the proper function of your fuel pump. 

An electric fuel pump works by using an electrical charge to move the diaphragm to create a vacuum and pressure system that pumps fuel from your tank into your carburetor or fuel injection system.

When the electrical grounding is bad, it can cause surging voltage or lowered voltage to improperly power the fuel pump. Because each item on the bike is rated for a certain voltage, these irregularities in current flow can cause that item or system to malfunction. 

Power surges that have nowhere to flow can overheat, short out, or completely destroy the fuel pump, in this case. 

Related: Motorcycle Clicks Instead Of Starting: 3 Reasons (Solved)

5. Hard Starting

These days, most motorcycles use an electric starting system. An electric starting system works by transmitting an electric current from the battery when the starter button or lever is switched on.

The electric current powers the starter motor, which turns the internal starter clutch. This revolution causes the motor to fire up, starting the engine of the bike.

If your grounding is damaged, it causes the kinds of voltage drops and surges that the starter system isn’t rated for.

Too low a voltage won’t be enough to power the starter motor and the bike will start erratically and invariably. 

Related: Motorcycle Won’t Kickstart | Here’s Why (Solved)

6. Damaged Electrical Wiring

One common cause of electrical grounding failure is damaged electrical wiring.

If your grounding system is already beginning to be faulty, then any power surge from the battery or electricity created by the movement of the motor can overheat the delicate wiring in your bike.

Overheated wiring can burn the thermoplastic or thermoset wire insulation, resulting in the opening of electrical pathways that should stay closed.

Even if your grounding system is still intact, having open access to the electrical system can cause new areas that should be grounded to become unprotected.

7. Dead Battery

Sometimes, when we have electrical problems, we buy a new battery to solve the problem.

But sometimes this solution doesn’t work, leaving us scratching our head why one of our electrical systems is experiencing failure.

If a grounding system is bad, it can cause voltage leaks. Voltage leaks are areas of connection or wiring that are damaged to ‘leak’ electricity out of the voltage line.

This both weakens the voltage flow of that system and electrifies systems on the bike not rated for any more electricity, or not rated for electricity at all.

If you continuously have to recharge a good battery by keeping it hooked up to a battery tender, it’s a good indication that you have bad grounding.

8. Bad Ignition Coil Function

The ignition coil is basically a transformer that uses electricity and magnetism to keep the battery running at the optimal voltage. 

When a bad ground affects the function of the ignition coil, it can cause the bike to run on a lower voltage than is needed to properly power the electrical systems. 

If your ignition coil isn’t grounded properly, it can cause sparking, which can cause some serious systemic malfunction.

Related: Motorcycle Won’t Start & Smells Like Gas (Solved & Explained)

How to Test Your Bike’s Grounding

All of the symptoms we have mentioned can be diagnosed by testing the grounding of your motorcycle.

You will need some simple tools and a voltmeter (any voltmeter will do, I tend to stay away from the multi-hundred dollar testers and instead use the cheap ones you can pick up for around $10-$15).

Although this is an easy diagnosis, it can be time-consuming. You will want to put the positive (red) probe on the red, positive battery terminal.

First test the battery by placing the black, negative probe on the negative battery terminal (a good motorcycle battery should be putting out 12.6-13.5 volts). 

Now that you have a good battery reading, start investigating several good grounding points on the bike for any voltage drop or fluctuation.

Once you find an area of the bike with drops or rapid changes in voltage reading, you know where to look for bad grounding. Trace back to the closest part of the grounding circuit and look for any problems with connections or damaged wiring. 

Replace this terminal or wiring to fix the grounding issue on your motorcycle!

Sources

Why Does A Circuit Always Have To Have A Ground | LearningAboutElectronics.com

Motorcycle Ignition Systems: What Are They And How Do They Work? | UTI.edu

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