I cannot think of a more disappointing or frustrating thing than a motorcycle that just won’t start.
Before you dig through this list of possible reasons your motorcycle won’t start, be sure to check your bike’s battery for the correct voltage.
Most motorcycles have 12v batteries. Make sure this is the case with your bike and then test the voltage with a voltmeter. A healthy battery reads somewhere between 12.6 and 13.5 volts.
Here’s What a Motorcycle Needs to Start:
Sometimes, even with a perfectly good battery, a motorcycle simply won’t start. That’s because for the motor to start, you need spark, air, and fuel. If you are lacking one of these things, the combustion that takes place in the engine simply won’t be happening.
It would be great if the only electrical component of the bike was a battery that shot electricity straight to the spark plug, but there are a series of electrical components that can malfunction or become damaged. We’ll look into that below.
If your airflow system isn’t allowing your bike to breathe properly from leaks in several different parts of the vacuum system, then a good battery won’t be able to save you from sitting on a dead bike in your garage.
Finally, the complex arrangement of the fuel line where it starts in the tank down to the combustion chamber can cause leaks, stoppages, or problems that prevent a motorcycle from starting even if there is plenty of electricity in the battery.
Your Motorcycle Might Not Start With a Good Battery
Myriad components of your motorcycle’s electrical, air, and fuel-delivery systems can contribute to a bike that has the correct voltage, but no way to start properly.
Electrical relays, grounding, shorts, damaged wires or spark plugs, major vacuum leaks, or stoppages in fuel delivery will keep your engine from properly combusting, and keep your bike right where it sits.
Fortunately, we’ve compiled a comprehensive list of reasons why your motorcycle won’t start if your battery is good.
A Very Common Problem: A Bad Starter Relay
To begin diagnosing the problems you may be having when a motorcycle won’t start right up at the push of a button, begin at the starter relay.
Essentially, the relay changes the incoming voltage from the battery and gives power to the starter motor.
Using a voltmeter, you can easily test the bad starter relay.
Locate your bike’s starter relay. Inside the relay is the solenoid- a coil that flips a switch when 12 volts are applied to it.
Here’s a very easy listening test to find out if the solenoid in the relay is bad. Hit the starter button. Do you hear a small snapping noise inside the relay? If you don’t, you will need to replace your relay.
Motorcycle Has Grounding Issue
A ground wire, or series of ground wires, is not as daunting as it may sound.
First, grounding wires offer up another electrical pathway for electrical current to flow if there is an overload of electricity in the system. It is essentially a fail-safe for your existing circuits, so that, in the case of electrical surging, it won’t damage the circuit.
A traditional grounding system like one you would find in your house connects to the earth via a metal rod pounded into the ground- hence, grounding.
Because motorcycles, by nature, need to move around, they have what is called floating ground. This means that the system is grounded to the bare metal frame of the bike.
Because of the relative complexity of motorcycle wiring harnesses, it is possible to have a short in the bike’s grounding.
There are several grounding points where the green grounding wire is connected to the frame. These are different on each make and model of bike, but there’s a good chance that the grounding points are under the tank and under the seat.
If there is any corrosion at the grounding point, be sure to disconnect the battery and scrub/scour/clean the connection.
Locate the grounding points and check their connections by attaching a test light or one leg of a multimeter to the battery and the other side to the grounding location.
If you get no light or no voltage reading, then you have a problem with the ground, and it will need to be repaired or replaced.
Bike’s Wiring Harness Is Shorted Out
Another reason a motorcycle won’t start, even with a good battery, is a shorted or damaged wiring harness.
This can be a painstaking process to go through all of your wiring, connectors, and relays, but it will probably be evident because it will affect other systems of the bike that will not be functioning properly.
A simple way to start testing the harness is to remove the seat and gas tank so you have a good view of the wiring harness. A visual inspection of the harness might show obvious signs of damage.
One sign might be burned or corroded wires within the harness.
Don’t worry though, this can be pretty simple to fix with some basic electrical tools. Any burned or corroded wire can be fixed without having to remove or replace the whole harness.
Having identified any damaged wire, disconnect the battery, cut the wire back beyond the damaged section, strip both ends, slide on a piece of a heat shrink tube, and twist or solder (solder is better!) the wire ends together.
Now slide the heat shrink tube back over the bare wire, heat shrink it, and reconnect the battery.
If your problem was a short in the wiring, this might get your bike to fire right up!
Bad Spark Plug Wires
Spark plug wires transfer the electricity from the starter coil to the spark plugs to create the spark needed for a combustion engine to work properly.
If the rubber-encased wire to the spark plug boot has gone bad, you won’t get the spark needed to combust the air/fuel mixture and fire the engine.
Most manufacturers recommend that spark plug wires be replaced every 8,000-10,000 miles, but the wires can go bad beforehand if they have been corroded or damaged from rough use.
Any wires that have cracked or corroded rubber, or corrosion at the ends of the wires signal you will need to replace them.
Alternately, you can use a voltmeter to Ohm out the wire and see if electricity can travel from one end to the other. If that is not the case, you will need to replace the bad spark plug wires with new ones.
Broken Or Tarnished Spark Plugs
If you have a good battery, but the bike just won’t start, it serves to pop out those spark plugs for an inspection.
Using a deep socket that is appropriate to your spark plug’s size and specifications, remove the plug or plugs from the engine head for a visual inspection.
If the spark plug tip is damaged, corroded, or covered in tons of black tarnish or white chalky tarnish, it’s time to replace them. The ceramic element of a spark plug can also crack or break, rendering them useless.
Make sure that you are getting spark before you go any further!
Fuel Filter Is Clogged
Yet another way that your bike’s fuel delivery might be impeded is clogging in the fuel filter. Most motorcycle fuel filters are right inside the bottom of the tank where it sits on the fuel valve.
If your bike won’t start and it’s a fuel issue, drain your tank and remove the fuel valve to find the fuel filter.
Over time, dirty or low-quality fuel can clog up the fuel filter. If this is the case, carefully clean it or consider replacing it.
Air Filter Needs Replacement/Cleaning/Oiling
A running motorcycle needs the holy trinity of air/fuel/spark to run properly. The air filter that covers your air intake is specifically made to allow the proper amount of airflow through.
If your airflow is impeded by collected debris, dirt, and dust, it won’t feed the correct amount of air into your air/fuel mixture created either in your carburetor or fuel jets.
Take a good look at your air filter. If there is a visible excess of detritus collected around the paper, mesh, or foam that makes up the filtration body, it’s possible your bike isn’t getting enough air to breathe.
A simple test can be done with any compressed air. Blow out the filter well, reinstall and try to start your bike. If it starts up, then you weren’t getting enough air.
Air filters are easy to maintain as well as cheap. If your bike won’t start because it’s not getting enough air, consider replacing them as often as the manufacturer suggests.
Check Your Fuel Injectors
While carburetors have some adjustments to finesse, fuel injectors often have over 30 minor adjustments to make them run smoothly and effectively.
If your fuel injection system has become clogged, you won’t be able to get enough fuel to your engine and the bike might not even start, even if your battery looks good.
Unfortunately, due to the complex nature of fuel injection systems, this is a diagnosis and solution for the professionals.
Have You Taken a Look At Your Fuses Lately?
Motorcycles, just like automobiles, have fuses. Disconnect your (good) battery at the terminals and open the fuse box.
Now go through the fuses one by one. If one happens to be blown, you can easily replace it with a fuse of the same rating. That’s why it’s good to have spare fuses on hand.
One thing to consider when a fuse has blown is that the circuit it is associated with might have been damaged, ungrounded, or become prone to surging.
Your service manual will have diagrams for what circuit each fuse is used for. Inspect that circuit for wear and repair any circuit necessary.
Damaged Vacuum Line
Motorcycles need exactly the right amount of air. To make sure that no extra air enters the system, causing idle, RPM, and acceleration problems, the whole air system is a ‘vacuum’-meaning that it is a sealed system.
While smaller vacuum leaks can create the aforementioned problems, any large leak in the air intake or rubber boots that run air from the intake to the engine can keep the motorcycle from starting at all.
Do a visual inspection of the whole air intake, airbox, rubber boots, and clamping. If there are large holes or tears, then too much air is getting into the system and the bike won’t start. Any damaged pieces of the vacuum line will need to be replaced to solve this problem.
Kickstand Prevents Bike From Starting
If you are on a newer bike for the first time, it’s a possibility that the kickstand itself is preventing the bike from starting. That’s because some new bikes won’t start if the kickstand is down.
Try sitting on the bike and booting up the kickstand. Does it start now? Presto!