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It’s an age old questions that’s left many riders scratching their heads: why won’t my motorcycle start?
There are all sorts of things that can cause your motorcycle to run poorly or not start at all.
This page will cover the common problems your motorcycle might have and how to troubleshoot and fix them.
Remember, always start with the simple solutions.
Another great rule to keep in mind: if you’re finding yourself getting frustrated and can’t figure it out – walk away from the bike and take a break. You may find the solution comes to you when you’ve had a chance to clear your head.
Simple Things to Check First if Your Motorcycle Won’t Start
Here are some of the simple, stupid and common things to check when your motorcycle won’t start:
- Make sure the kill switch is in the correct position.
- Check that the battery is charged.
- Check that there is enough fuel and the petcock is on.
- Make sure the bike is in neutral.
- Engage the clutch, if your bike is equipped with a clutch trigger to start.
- Make sure your intake and exhaust is not clogged.
- Make sure the spark plugs wires are attached.
If those things check out, continue reading for more tips on getting your motorcycle started.
They may seem simple, but they happen more than you’d think. There’s nothing worse than taking apart your carbs of dismantling your engine only to find that the kill switch was off or the spark plug wires were loose.
Save yourself the necessary work and check the simple things first!
Diagnosing the Problem: “My Motorcycle Still Won’t Start!”
Ok, so you’ve checked the simple list above and your bike still won’t start. Now it’s time to start diagnosing the issue.
Remember, all a motorcycle engine needs is fuel, air (compression), and spark.
If it has those 3 things, it should run. It might not run well, but you’ll be able to tune it once you’re able to diagnose what’s going on.
1. Check the Compression
When troubleshooting a motorcycle, it’s always a good idea to begin with checking the compression in the cylinders.
Remove the spark plugs and hook up a compression gauge. Turn the engine over and check the readings. Proper compression may vary slightly by bike, but it should read around at least 100 PSI for it to run.
If the compression readings are too low, you’re going to have a hard time getting the motorcycle to start.
If the compression readings are good, move on to step 2 and check for spark.
2. Check the Spark
With a brand new spark plug, set the gap to at least 1/4″ or the plug gap recommended in your service manual and set the plug on the cylinder head to ground it.
Push the starter button or kick the kickstarter and watch the spark plug.
If you see a strong blue spark jump from the electrode, your spark is solid and you can move on to checking the fuel delivery.
If the spark is weak or there is no spark at all, check that the battery is fully charged and go through all the electrical connections.
When the motorcycle has good spark and a full battery, you may need to inspect the ignition system itself (points or electronic).
3. Check the Fuel Delivery & Air Circuit
With good spark and compression, it’s time to troubleshoot the carburetors.
Any old motorcycle that has been sitting for a long time is likely to have some gummed-up or varnished carbs.
If fuel delivery proves to be the issues, a thorough carb cleaning can usually solve the problem.
If the motorcycle engine starts, but will only continue running with the choke on, the idle jets are likely clogged.
When the motorcycle won’t start at all, then either the fuel needle/seat or the petcock is clogged shut or stuck. If you’re able to start the engine with a little bit of gasoline or starting fluid down the spark plug hole, there is mostly likely a problem somewhere along the fuel delivery line – from the petcock to the needle valve.
Once you can start it up, you’ll be ready to tune it to a roadworthy condition.
Common Causes and Solutions When Your Motorcycle Won’t Start
Now that you understand the basics of why your motorcycle won’t start, you’ll be ready to dive deeper into the root cause.
After you’ve determine which main category the issue falls under, you’re that much closer to fixing the problem and getting your bike running again.
Motorcycle Battery Issues
If your fuel/air delivery is good and your bike has decent compression, you’ve likely narrowed it down to an electrical issue.
Checking that the battery has enough charge is a good place to start.
Signs that your battery may not be carrying enough charge include:
- Dim or weak lights.
- Weak or no action from the starter motor.
- Weak or non-existant spark.
First, take a look at the battery to make sure it is in good visual condition, the connections are solid, and all the fluid levels are good.
Next, you’ll want to grab your multimeter to check the voltage reading. The voltage should read close to 12.6 volts.
If the voltage reads slightly under 12.6, you should give it a charge and try again.
If the voltage reading is well below 12, you’ll likely need to replace the battery.
If you’re in a pinch, you may be able to start your motorcycle with a push start or bump start.
Loose Wires or Blown Fuses
Another electrical issue that may cause a no-start scenario can be loose wiring connections and blown fuses.
If the battery is good and there aren’t any other obvious electrical issues, you should take a look at your electrical connections and fuse box to make sure everything is solid.
A blown fuse or poor connection can throw a wrench in your bike’s entire electrical system.
If you trace the issue to a blown fuse, you can try to start it again. If the fuse continue to blow, you’ll need to trace down why. This could include poor grounding, an overloaded circuit, or a faulty connection somewhere.
Bad Starter Motor
If your bike only has an electric start, it is possible for a dead starter motor to be the source of the problem.
You’ll know your starter may be bad if you experience any of the following:
- A clicking sound when you press the starter button.
- A high-pitched whirl.
- Nothing happens at all.
If you trace the issue to the starter motor itself, it will usually need to be replaced.
Learn more about testing your starter motor here.
Worn or Dead Spark Plugs, Wires, or Caps
A simple, but sometimes hard to trace fix for a no start condition can be that your motorcycle’s spark plugs are bad.
Spark plugs can go bad for a number of reasons, including:
- Fouled plugs from a rich condition.
- Burnt plugs from running lean.
- Damaged plugs from being hit or dropped.
Your spark plugs might be bad if your motorcycle:
- Engine floods.
Spark plugs do deteriorate with age and should be replaced periodically.
Improper plug gap can also cause issues.
Fouled plugs or plugs that have been run too lean and have burnt out should be replaced as well.
Lean and rich conditions will wear down your spark plugs faster.
Generally, spark plugs should be replaced every 5 years.
If the spark plugs are the likely issue, simply replace them and try to start up your bike again.
Learn more about reading the color and condition of your spark plugs with our spark plug color chart.
Additionally, you’ll want to inspect the spark plug wires and caps to make sure they’re in good condition too.
Bad Ignition Coils
If you know the issue is electrical and everything else checks out, your ignition coils could be the problem.
Bad ignition coils can cause a situation in which no spark or too weak of a spark to reach the plugs.
Ignition coils can be tested with a multimeter.
Refer to your motorcycle service manual for the ohms readings you’ll be looking for.
If the ignition coils fall outside of the serviceable ranges, you’ll need to replace them.
Ignition Timing Issues
If your motorcycle ignition timing isn’t set correctly, it won’t be able to deliver the spark at the correct time during the engine’s combustion cycle.
Symptoms of poor ignition timing can include no start situations or situations where the bike will start, but die quickly or under load.
Refer to your motorcycle shop manual for how to set your ignition timing.
Dirty or Clogged Carburetors
If you determine that your carbs need cleaning, you’ll need to remove them from the bike and take them apart.
Overtime and after a bike has been sitting for a while, gunk, debris, and fuel varnish can clog up the jets and tiny passages inside the carburetor.
The result is an incorrect ration of fuel/air when the engine turns over.
Your carbs likely need to be cleaned and tuned if you experience any of the following:
- Rich conditions.
- Lean conditions.
- Bike won’t start.
- Loss of power during acceleration.
- High ideal.
- Gas leaking from the float bowl.
Clogged Air Intake
A clogged intake will lead to a situation in which too little air is getting to the combustion chamber.
This situation may make it difficult to start the bike or to keep it running for very long.
Remove your air filer and check the area around the intake for any obviously obstruction.
It may simple be that your air filter elements needs to be cleaned.
Low Compression on a 4-Stroke Motorcycle Engine
When the compression readings are too low on a 4-stroke motorcycle engine, check the valve clearances to make sure there are within spec as per the shop manual. If the valves are too tight, you may be loosing compression.
If the motorcycle’s valves are within the proper clearance, you’ll likely need to rebuild the top end.
Low Compression on a 2-Stroke Motorcycle Engine
If the compression readings are too low on a 2-stroke motorcycle engine, the piston rings may not be sealing properly. You may need to rebuild the engine.
Seized Motorcycle Engine
If your bike has been running fine and has only recently decided to not start, a seized engine is probably not your issue.
However, if you’re working on a motorcycle project that has been sitting for a while, it’s possible that the engine is seized.
This means that something has made it so the engine can not physically turn over and the pistons won’t move.
Unfortunately, the fix for a sized engine is an engine rebuild.
Your engine might be seized if the starter clicks, but doesn’t rotate the engine or if the kick starter feels stuck in place.
Engines can seize:
- If they’re oil starved.
- If they’ve been sitting for too long.
- If the oil is contaminated.
A seized engine warrants a full engine rebuild.
To free a seized piston, allow it to soak in penetrative lubricant or diesel fuel.
A piece of wood can be used to strike a stuck piston when the head is removed.
Cylinders may need to be bored and honed as a result of a seized engine.
Troubleshooting Other Problems with your Motorcycle
If you’ve got your bike to start, but are still noticing some other issues, the motorcycle will not be able to operate a peak performance until those issues are addressed.
Below, we’ve compiled a list of some of the most common questions and issues riders run into, along with some direction of what you’ll need to do next to fix it.
Why Does My Motorcycle Backfire?
A backfire describe the loud bang or pop that comes from your motorcycle’s exhaust.
Motorcycle backfire can be caused by:
- Improper timing.
- Fuel mixture is too rich.
- Fuel mixture is too lean.
- Compression is too low.
- Poor spark.
- Improper exhaust pipes for the bike.
Why does my Motorcycle’s Oil Leak?
Oil leaks can be caused by:
- Bad gaskets/uneven gasket surfaces (most common).
- Loose engine bolts.
- Worn engine case seals.
- Oil pan drain plug.
- Cracked engine case.
You’ll want to find the source of the oil leak as soon as you can and fix the problem.
Why is my Throttle Sticking?
Your throttle is likely sticking due to either:
- Improperly adjusted throttle cable.
- Broken throttle cable.
- Improperly lubricated throttle cable.
My Motorcycle Clicks, but Won’t Start
If your motorcycle is clicking when you hit the starter, but the bike won’t start:
- Your battery might be dead (most common).
- Your starter might be bad.
- Your engine may be seized.
The first step will be to charge up your battery and try again.
What Happens if I Run out of Gas?
If you run out of gas, here’s what will typically happen:
- The bike will begin to sputter.
- You’ll lose power.
- The bike won’t start.
If you’re lucky, you’ll still be able to switch the petcock, or fuel valve, to the “Reserve” position and get yourself to a gas station.
Why Does My Motorcycle Battery Keep Dying?
If your battery keeps dying, you may have:
- An old/dead battery.
- An undercharged battery.
- Bad connections.
- A bad stator.
- A broken regulator/rectifier.
Confirm whether or not the battery is dead and replace it if necessary.
What Happens if my Engine is Flooded?
You’ll flood the engine if there is not adequate spark to ignite the fuel mixture. First, make sure the bike is on. Next, check your spark plugs for proper plug gap and a good spark.
If you flood your motorcycle:
- Wait before trying to start it again.
- Turn off the fuel valve and the ignition.
- Remove the spark plugs.
- Crank the engine.
My Motorcycle Stalls When I Accelerate
If your motorcycle stalls on acceleration, you may have:
- Clogged or blocked carburetor passages.
- Improper fuel level.
- Improper timing.
- Vacuum leak.
- Broken throttle cable or spring.
- Too rich or too lean a mixture.
My Motorcycle is Leaking Gas
If your motorcycle is leaking gas, here’s what you should check:
- Fuel hose fitting and connections.
- Floats, float needle, and float bowl gasket.
- Float bowl height.
- Petcock/fuel valve.
- Gas tank.
My Motorcycle is Overheating
A motorcycle that overheats may be caused by:
- Too high of an idle.
- Too lean of a fuel/air mixture.
- Improper coolant levels.
- Too hot of temperatures with no moving (i.e. air-cooled engine stuck in traffic).
Is My Clutch Bad?
Clutch baskets that have been sitting for a long time tend to bind together and not function properly.
Your clutch might be bad if:
- Your engine revs unexpectedly.
- You gas mileage is bad.
- The clutch lever is stuck.
- Shifting is difficult, jerky, and loud.
Is My Bike Running Lean?
Running lean means there is too much air in the fuel/air mixture. Symptoms of a lean condition include:
- Poor idle.
- Poor acceleration.
- High RPMs.
- Higher heat from the exhaust.
- White/colorless spark plugs.
Lean conditions can be fixed with a more restrictive air filter or adjusting or rejetting the carbs.
Is My Bike Running Rich?
Running rich means there is too much fuel in the fuel/air mixture. Symptoms of a rich condition include:
- Black exhaust smoke.
- Black or dark brown spark plugs.
- Poor acceleration.
- Flooded engine.
Rich conditions can be fixed with a less restrictive air filter, adjusting the carbs, or rejetting the carbs.
Learn more about running lean vs. rich.
My Bike has a High Idle
A motorcycle with a high idle is typically caused by:
- Carbs that are out-of-tune.
- Idle screws out of adjustment.
- Lean mixtures.
- Vacuum leaks.
- Stuck throttle or throttle cable.
Why is my Motorcycle Smoking?
Smoking can be caused by a number of issues include:
- Lean mixture.
- Rich mixture.
- Leaking valves.
- Worn pistons.
- Oil leaks.
- Electrical issues.
You can typically diagnose the cause of the smoke by it’s color and where it comes from:
- Smoke coming from the engine cases may indicate an oil leak.
- Smoke from anywhere other than the engine or exhaust may indicate an electrical issues.
- Dark, grey, or blue smoke indicates too rich a mixture or burning oil.
- White smoke may simply be normal condensation burning off, coolant leaking into the combustion chamber (sweet smell), or excess oil.
My Motorcycle’s Exhaust Pipes are Blued
If you notice that your motorcycle’s exhaust pipes are blue, it’s an indication of too much heat.
This can often be caused by a lean condition.
Why Does my Motorcycle Wobble at High Speed?
If your motorcycle wobbles at high speed you may have:
- Worn tires.
- Improper tire pressure.
- Worn wheel bearings.
- Worn steering bearings.
- Loose axle nut.
If you experience this while you’re riding:
- Ease off the throttle.
- Hold the handlebars firmly.
- Lean forward over your tanks.
- Gradually slow until you regain control.
My Motorcycle Pulls to One Side
Your motorcycle may pull to one side if:
- The tires are uneven.
- Alignment between forks and handlebars is off.
My Motorcycle is Sputtering
If your motorcycle is sputtering or feels jerky, you may have:
- A lean condition.
- A vacuum leak.
- No gas or improper fuel level.
- Bad spark plugs.
- Improper timing.
Do I have a Vacuum Leak?
A vacuum leak is caused by extra air entering the combustion chamber. Leaks are often caused by hard, cracked rubber carb/manifold boots or bad o-rings/washers.
Signs of a vacuum leak include:
- Racing RPM.
- Loss of power.
- Dies with no choke.
- Sporadic idle.
You can identify the exact source of a vacuum leak by running the engine and spraying some carb cleaner around the carbs and carb boots.
My Bike Dies When the Choke is Off
If your motorcycle only runs with the choke on, it might be time to clean your carbs.
Motorcycles that will only run with the choke on typically indicate a clogged pilot jet.
There is a Knocking Noise in my Engine
Engine knocking is typically caused by one of the following issues:
- Improper timing.
- Warped cylinders.
- Worn bearings and guides.
- Valve-piston contact.
- Broken transmission.
If your engine is knocking, perform a full tune up and see if it fixes the problem. If not, you’ll need to take the engine apart to find the problem.
Why is my Motorcycle Vibrating?
Unexpected vibrations may be caused by:
- Uneven tires.
- Sticking brakes.
- Bent rim.
- Improper timing.
- Worn bearings.
- Worn pistons or cylinders.
Be sure to check out our articles in our motorcycle maintenance sections to get your bike back on the road.