Bad Boy Lawn Mower Won’t Start

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Ready to mow but your Bad Boy lawn mower won’t start? Don’t call the technician just yet because it is a common Bad Boy mower problem.

Read this article until the end to learn about the fixes some other Bad Boy lawn mower owners with similar issues have used to get their mowers working again.

But before we get into that…

Some of the reasons a Bad Boy lawn mower won’t start include:

  • No fuel in the fuel tank
  • Bad or old fuel
  • Faulty Fuel Cap
  • Clogged air filter
  • Dirty carburetor

Bad Boy Lawn Mower Won’t Start: Causes and Solutions

1. Bad Boy Zero-Turn Mower Broken Flywheel Key

The flywheel key is a small metal piece that keeps the flywheel and crankshaft aligned when you tighten the flywheel nut.

The mower’s engine may suddenly stop if the zero turn mower blade hits a hard object. 

If this happens, it breaks to protect parts such as the crankshaft from getting damaged.

For instance, a broken flywheel key may prevent your Bad Boy zero-turn mower from starting. 

To check if the flywheel is broken, remove the flywheel and inspect the flywheel key.

Fix: Replace the broken flywheel key.

2. No Fuel in the Fuel Tank

Another main reason why your Bad Boy mower won’t start is if your tank is empty. 

Empty fuel tanks can halt operations, cause below par performance and make rough sounds.

 It is important to always check your fuel level regularly before you start the mowing machine.

Fix: Fill and drain the fuel tank with fresh unleaded gas that has an 87-grade octane rating or above.

Avoid using gas that has more than ten percent ethanol content. It is also important to buy high-quality fuel to ensure maximum performance.

3. Old or Bad Gas 

Using a bad or old gas in your Bad Boy mower can prevent it from starting. Gas may begin to deteriorate or become ineffective after thirty days.

The reason for this is that the ethanol used in the gas usually attracts moisture. In this case, the moisture evaporates and leaves a sticky residue that can block the fuel system.

It is advisable to buy your gas from a fast-selling petrol station. In addition, ensure that you make use of it within thirty days.

You can also add a fuel additive to stabilize the fuel if you can’t finish it within the specified time frame.

Fix: Use a fuel siphon pump to take out the old fuel from the tank.  To clean or remove moisture from the fuel system, you need to add fresh gasoline and a fuel additive.

4. Faulty Wiring and Loose Connections

One of the main reasons why your Bad Boy mower won’t start is faulty wiring and loose connections.

Fix: Check for all visible wires and connections for breakage and damage. For instance, you may check the condition of the wiring harness ground cable.

In most models, it is located inside the right side of the mower. Ensure that the ground is clean, tight and connected.

5. Defective Spark Plug 


A defective spark plug may result in Bad Boy starting problems. 

Unwanted carbon buildup and oil around the spark plug may develop starting issues. This problem is common with the Bad Boy MZ Magnum.

Use a spark plug tester to check for defective spark plugs. If there is no spark, it means that the spark plug is faulty and it needs to be replaced.

Fix: Inspect the spark plug for signs of a broken porcelain insulator or carbon buildup. 

You can also replace the defective spark plug. Use a feeler gauge to check if it is properly gapped.

6. Clogged Air Filter 


For optimal performance,  your mower engine requires proper airflow to operate.

Dirty air filters can deprive your engine of adequate air which may result in overheating and can also cause serious engine damage.

FixUse a mild soap and cloth to wipe off excess dirt and oil in the air filter . Ensure that you do not clog it with loose dirt. 

Note: Do not use an air compressor to clean the air filter. It deteriorates the mower’s level of performance.

7. Clogged Fuel Filter

A fuel filter helps to prevent debris and dirt from entering the engine of your Bad Boy mower. 

Clogged fuel filters can jeopardize the health of your Bad Boy mower engine.

The signs of a clogged fuel filter include smelly fumes, no engine power and engine misfiring.

The engine of your Bad Boy mower may also stall when accelerating. It is best to replace the fuel filter if you notice all these signs.

Fix: Replace the defective fuel filter with a new one if you discover that there is a stoppage of fuel flow at the fuel filter.

8. Bad Boy Riding Mower Won’t Start because of a Faulty Fuel Pump

If your Bad Boy riding mower won’t start, it might be due to a faulty fuel pump.

The Bad Boy fuel pump has three ports (the gas in port, gas out port and pulse port) and two small check valves on the input and output ports. 

Your fuel pump may malfunction over time. This problem can be related to bad or fuel gas.

Fix: Inspect the fuel pump for cracks. Use a fuel shut-off valve to control the fuel flow of your Bad Boy riding mower.

Inspect the fuel filter or line for restrictions. Once you notice that the pump is getting fuel, check to be sure that the fuel is pumped out properly. 

Replace the fuel pump if the problem persists.

9. Loose Terminals or Bad Battery 

A mower’s battery needs to be fully charged to enable the mowing machine to start with ease. 

If the cables are loose, it can result in starting problems. This is common with Bad Boy MZ Magnum and MZ Rambler riding lawn mowers.

Fix: You can use a multimeter to test the battery. Get a reading of about 12.7 volts. 

You may need to charge the battery if the level is lower than 12.7 volts.

Replace the battery with a new one if it does not hold a charge.

10. Clogged Fuel Line

Old fuel might block the mowing machine’s fuel line. This will cause the engine to sputter and result in the mower not starting.

Other signs that may arise include smoke coming out from the machine or its engine switching off.

Fix: The first step to take is to inspect the fuel line to see if it is clogged. 

Take off the fuel line, and use a spray carburetor cleaner to clean the choke plate so that it can move freely.

You can also remove the dirt and sticky residue with compressed air. 

Regardless of this, it is best to replace the fuel line with a new one.

11. Clogged and Dirty Carburetor Causes Bad Boy Riding Mower Not to Start


A clogged or dirty carburetor is mostly caused by leaving the fuel in your mower for an extended time. 

This issue is common with the Bad Boy MZ Rambler riding lawn mower.

Over time, some ingredients in the fuel evaporate and leave behind the stickier and thicker substance. 

This will clog up the carburetor which will fail to regulate the fuel that the engine receives, causing your engine not to start.

Fix: Clean the carburetor or replace it if it is in very bad condition. 

If you know that you can’t handle this task, it is advisable to seek the help of a professional to assist you in fixing it.

12. Defective Ignition Coil

The ignition coil works as a source for the spark plug to acquire voltage from the battery. 

A defective ignition coil may prevent your Bad Boy mower from starting. This happens when an improper ground wire connection to battery voltage fails.

Fix: The first step to take is to verify if the spark plug is functioning properly. Use an ohmmeter to check its continuity.

Furthermore, change the defective ignition coil if there is a break in the continuity.

13. Bad Boy Zero-Turn Mower Faulty Safety Switch

Safety switches help to turn off the engine when the mower deck is engaged and when the rider gets off the seat.

In addition, the safety switch provides vital protection by stopping the rotary blades from turning.

When this switch fails, your Bad Boy riding zero turn mower may no longer start.

Fix: You should replace the bad switch with a new one.

Note: It is advisable not to operate your Bad Boy riding mower without installing the safety switch.

14. Bad Ignition Switch

A bad ignition switch may stop your Bad Boy mowing machine from starting.

It is important to get a multimeter to test it to confirm if it is not working properly.

Fix: The simple way to fix this is to replace the bad switch.

15. Faulty Starter Solenoid

The starter solenoid is similar to a one-time switch that turns on the engine’s starter motor.

A hum or click when turning the ignition key indicates that you should inspect your Bad Boy riding mower’s solenoid. 

Another sign of a bad solenoid is if it becomes hot and starts to melt or smoke.

Fix: Replace the bad solenoid with a new one.

16. Incorrect Operating Procedure

Bad Boy mowers are equipped with safety features that prevent them from starting unless you adhere to the procedures starting them.  

Fix: Check the mower’s manual to be sure that you are using the machine properly so that you don’t set off safety systems that can prevent your mower from starting.

17. Bad Charging System

A faulty charging system may cause mower starting problems. 

This problem can be related to a bad alternator, stator or issues with other electrical components of your Bad Boy lawn mower.

Fix: It is advisable to seek the help of an expert to help you to identify the faulty part of the charging system.

18. Faulty Start Switch

A faulty start switch may also cause your mowing machine not to start. This affects the performance and functionality of your Bad Boy mower. 

To determine if it is faulty, you need to use a multimeter to test it for continuity.

Fix: Replace the bad start switch with a new one.

19. Faulty in-line fuses

Faulty in-line fuses may cause your Bad boy mowing machine not to start. In-line fuses are installed in the path or line of a circuit.

 If they are faulty, they can affect the functionality and performance of the mower.

Fix: Check in-line fuses and replace them with new ones.

20. Faulty Fuel Cap

A faulty fuel cap may cause your Bad Boy mowing machine not to start. This component comes with a vent. 

When the vent gets clogged, a vacuum is created in the fuel tank and this prevents the machine from drawing gas out of it.

To verify this problem, you may need to remove the cap and start the mowing machine. 

  • If it starts, try to re-install the fuel cap while the machine is still operating.
  • After that, wait for some time to check if it will sputter or die again. 
  • If the Bad Boy machine dies or sputters, it means that the fuel cap is faulty.

Fix: Replace the faulty fuel cap.

Bad Boy Mower Won’t Start When Hot

If your Bad Boy mower won’t start when hot, the problem may be as a result of the following:

  • Engine overheating
  • Faulty spark plugs
  • Defective carburetor
  • Compression Problem

Troubleshooting Tips

  • Allow the engine to cool down, and clean out the fins and the underside of the shroud.
  • Replace faulty spark plugs and carburetor.
  • Contact a professional to help you troubleshoot the compression problem

Bad Boy Mower Won’t Start After Winter

If your Bad Boy mower fails to start after winter, it may be as a result of the following reasons:

Faulty Carburetor

The old gas in your mower may clog the carburetor. It can also enter the float bowl, making the mower not start after winter.

Fix: Disassemble the carburetor and clean it with a carburetor cleaner. 

You may also replace the entire carburetor if you are unable to clean it effectively.  

Flat Battery

The battery of your Bad Boy mower is bound to be flat after sitting idle for a while

This battery will lose power because it hasn’t been charged during the winter period.

Fix: Put the battery on charge and ensure that the terminals are clean. 

You may need to replace it if the battery doesn’t hold a charge.

Bad Spark Plug

A bad spark plug is also one of the reasons why the mower won’t start after winter. 

Ensure that you use a spark plug tester to check if it is faulty. If there is no spark, it means that the spark plug is faulty.

Fix: Replace the faulty spark plug with a new one.

Bad Boy Mower Won’t Start After Running Out Of Gas

If your Bad Boy mower won’t start after running out of gas, the most likely problem is a dirty carburetor.

Other causes may include faulty auto-choke, contaminated gas, and a defective carburetor.

Troubleshooting Tips

  • Clean the carburetor or replace it if it is in very bad condition.
  • Check if the auto-choke is functioning properly. Ensure that you put it in the correct position.
  • Drain the old gas and add a fresh one.

Bad Boy Mower Won’t Start Without Starting Fluid

If your Bad Boy lawn mower won’t start without using starting fluid, you could be dealing with a faulty spark plug, dirty carburetor, old fuel, or clogged air filter.

These are likely problems that may happen to your machine especially if your Bad Boy mower has been sitting dormant all winter long.

Troubleshooting Tips

  • Clean the carburetor with a carburetor cleaner or replace it if it is in very bad condition.
  • Replace the faulty spark plug with a new one.
  • Use a fuel siphon pump to remove the old gas from the tank. You may need to add fresh gas and a fuel additive.
  • Clean the air filter with water and dish detergent to remove dirt or grease. 

Bad Boy Mower Won’t Start but Relay Clicks

If your Bad Boy mower won’t start but its relay clicks, the problem may come from the starter solenoid or faulty switch.

Fix: Replace the starter solenoid and faulty switch with new ones.

Bad Boy Riding Mower Clicks But Won’t Start

If your Bad Boy MZ Magnum or any other Bad Boy riding mower clicks but won’t start, the problem may be from the starter solenoid.


The most likely causes of solenoid clicking include low voltage, corroded or loose cable connections between the battery to the solenoid, or loose connection between the solenoid and starter. 

Furthermore, you can also check for a corroded connection between the battery ground circuit to the tractor frame. 

Troubleshooting Tips

  • Charge or replace the battery to fix the issue of low voltage.
  • Inspect connections, remove corrosions and re-establish good electrical contact to fix loose connections.
  • Check for faulty solenoid and replace it with a new one.
  • Check for the defective starter or any other mechanical issues with the engine

Where Are The Fuses On A Bad Boy Mower?

The 25-amp main fuse is located about three inches from the engine’s starter on several commercial engines (27 hp and above).

For small and light-duty commercial Bad Boy Boy mowers, the 25-amp main fuse can be found behind the battery connected to the starter solenoid.  

How Do I Know If My Bad Boy Solenoid is Bad?

The solenoid of your Bad Boy riding mower may be bad if you notice a hum or click when you turn the ignition key. This causes your mowing machine not to start.

Another symptom of a bad solenoid is when the wire gets hot and begins to melt or smoke. 

To diagnose a bad solenoid, you need to follow these steps:

  • Ensure That Your Battery Has A Full Charge.

Use a voltmeter to ensure that the battery has at least 12.3 volts in it.

  • Get Your Mowing Machine Ready To Start

To do this, you need to set the parking brake, put the machine in neutral and turn the key to the “on” position.

  • Use A Screwdriver To Bypass The Starter Solenoid

You can use a screwdriver to bypass the starter solenoid. You need to look for the cable from the battery and the cable to the starter. 

This may result in a spark when your screwdriver makes contact with these cables.

There is an indication that the solenoid may be bad if the engine turns over when you have bypassed the solenoid. 

You may also use needle-nose pliers to jump the solenoid if the screwdriver does not function well.

  • Test the solenoid

You need to take off the starter from the engine to test the solenoid with a battery charger. 

Once you have done this, attach the negative clamp to the starter’s case and touch the positive clamp to the big post and exciter wire on the solenoid.

How Do I Know if My Bad Boy Starter is Bad?

A faulty starter may show signs of a clicking sound when you press the ignition button, a cranking sound without the engine turning over, or when the mowing machine fails to start.


If your Bad Boy mower isn’t starting, the first step to take is to figure out the causes. 

In this article, we have shared some of the possible causes such as defective spark plug, bad fuel pump, clogged air filter and faulty fuel cap. 

Follow the recommended fixes to get your Bad Boy mower working again. If your mower still refuses to start after implementing the tips in this article, it might be best to seek a technician’s help.

Top Recommended Handy Tools for Troubleshooting & Servicing Your Lawn Mower

Multimeter – This is useful for checking voltage, continuity & current to identify electrical problems in your mowerFilter Wrench – For loosening your mower’s filter.
Carburetor Cleaner – Choke and Throttle Body Cleaner for cleaning clogs & buildup in the fuel system.Blade Balancer–Balances Blades After Sharpening.
Fuel Stabilizer – This stabilizes & cleans your fuel to reduce fuel system buildupBattery Inflator – This helps to ensure your mower tires stay inflated to prevent steering or uneven cutting issues.
Socket & Allen Wrench Set – These tools are needed to service & troubleshoot your mower problemsTachometer– Evaluates your mower’s engine performance and provides accurate data about the status of the engine
12-Volt Battery Charger – This is useful for charging your mower battery.Lawn Mower Blade Sharpener– Adjustable Lawn Mower Blade Sharpener for Right and Left Hand Blades.