Bad Boy zero-turn mowers lose power and bog down when old fuel causes fuel restrictions, the engine is overworked or not performing, or sufficient air isn’t getting to the engine.
The loss of power may be due to a dirty carburetor, plugged fuel filter, plugged air filter, dirty spark plug, wrong engine oil level, dirty cooling system, plugged mower deck, or old gas.
Follow the safety precautions in your Bad Boy operator’s manual. Remove the ignition key and spark plug boots before you begin making any repairs.
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Follow all safety instructions provided in your equipment operator’s manual before diagnosing, repairing, or operating. Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.
11 Reasons Your Bad Boy Zero Turn Mower Has No Power
1. Old Gas
Most gas sold today includes ethanol. This is an alternative fuel that can cause problems for the small engine on your Bad Boy zero-turn.
Ethanol attracts moisture from the air to the fuel system. The water and ethanol mixture isn’t only corrosive to mower parts, but it also leaves behind varnish that causes fuel restrictions resulting in a loss of power.
Because of this, only purchase the amount of fuel you are able to consume within 30 days before it starts to break down. Add a fuel additive to keep gas stable longer and reduce moisture in the fuel system.
SOLUTION: Drain your bad fuel into a container for recycling. Refill with fresh fuel. Gasoline-powered Bad Boy mowers use unleaded gasoline that has a minimum 87-octane rating and a maximum ethanol content of 10%.
Do not use a fuel with a higher ethanol content because ethanol is not good for small engines. Learn more about the right fuel to use in your Gravely zero-turn and stabilizing your fuel with an additive in my other articles.
2. Dirty Carburetor
The carburetor regulates the amount of fuel that is mixed with air for combustion. The substances left behind from running gas can clog fuel passageways keeping the engine from getting the proper gas-to-air mixture.
When this happens, the dirty carburetor can cause your mower to experience a loss of power. Clean a carburetor that isn’t allowing fuel to get to the cylinder.
SOLUTION: Before you tear your carburetor apart to clean it, confirm you are getting fuel to the carburetor. Next, remove the air filter and spray carburetor cleaner into the air intake.
Start the engine to see if it runs better. If the engine runs strong and then begins to lose power or die, you need to clean your carburetor. Refer to the article to find step-by-step instructions to clean your zero-turn carburetor.
3. Clogged Fuel Filter
Dirt and the substances left behind by running old fuel can clog the fuel filter. A good flow of fuel will be unable to pass through it so the engine receives the gas it requires for the engine to perform at its best.
This fuel restriction can cause your Bad Boy zero-turn to feel a loss of power and run sluggishly.
SOLUTION: Replace a clogged inline fuel filter with a new filter. Replace this filter annually to keep it in good condition.
4. Clogged Fuel Line
Clogs in the fuel line can also restrict fuel. Check for restrictions in the fuel lines by starting and stopping fuel flow using the fuel shut-off valve located on the bottom of your fuel tank or by crimping the fuel line.
Stop the fuel flow. Remove the end furthest from the fuel tank of one section of the fuel line and place it in a container. Start flow to check for blockages. Continue checking other sections of the fuel line as needed.
SOLUTION: When you find a clogged fuel line, remove the section of the line and spray carburetor cleaner into the line. This should help loosen up the clogs.
Follow this by blowing compressed air through the line to free the obstruction. If you cannot remove the blockage or you notice your line is dry and cracked, replace it with a new fuel line.
Check the fuel filter and replace the plugged filter.
5. Clogged Air Filter
When your engine isn’t able to get the right amount of air, you may experience a loss of power. A plugged air filter can cause this to happen.
The filter is used to keep dirt and other contaminants out of the air intake so it doesn’t damage the engine. It must be regularly cleaned or replaced so it doesn’t build up so much dirt that air isn’t able to pass through the filter.
Check the air filter. Going forward, I recommend replacing the air filter annually and cleaning it several times throughout the mowing season.
If you use your Bad Boy mower for commercial reasons or more than the average homeowner, the filter needs to be replaced or cleaned more often.
SOLUTION: Inspect and clean a dirty air filter. If it is extremely dirty or damaged the filter must be replaced with a new one.
How to Clean Your Bad Boy Zero Turn Paper Air Filter Element
- Remove the air filter from the air filter housing.
- Wipe out any remaining dirt in the housing with a dry cloth. Be careful not to allow dirt to fall into the air intake.
- Tap your air filter against a solid surface to knock as much dirt loose as possible.
- Hold your filter up to a light source.
- Reuse your filter if you can see light through the paper element and it is not damaged or extremely dirty. Otherwise, replace it with a new air filter.
6. Fouled Spark Plug
A fouled spark plug in your zero-turn can cause an intermittent spark resulting in a loss of power. Inspect your spark plug for signs of carbon buildup, wear, or damage.
SOLUTION: If you find a dirty or damaged spark plug, I recommend replacing it with a new one to ensure you’re running a good plug in the mower.
If you choose to, you can attempt to clean it with a wire brush and reuse it if the spark plug is in good condition and not very dark in color.
Make sure the electrode gap meets the specifications of the engine manufacturer and the spark plug wires are securely attached.
7. Low Engine Oil Level
When your Bad Boy zero turn doesn’t have enough engine oil in the crankcase, the engine will experience a loss of power. The lack of lubrication from not having enough oil causes increased friction.
This friction builds heat and causes the engine to get extremely hot and suffer a loss of power.
If a low engine level isn’t caught quickly, the increased heat will cause internal engine parts to melt. This can result in a significant engine repair bill or possibly an engine replacement.
Routinely check your engine oil level before each mowing. This doesn’t take too much time and can help you catch oil leaks or engine problems early.
Always run the correct amount of oil in your engine. Not doing so can cause running and overheating problems.
SOLUTION: When you find your engine doesn’t have enough oil, add oil to bring the level to the manufacturer’s recommended level.
If you continue to have engine problems, running your zero-turn mower with low engine oil could have caused internal damage that needs to be diagnosed by an experienced small engine mechanic.
8. Too Much Engine Oil
Overfilling the crankcase with engine oil will cause your engine to smoke. Increased pressure builds as a result of too much engine oil and oil can be pushed into the cylinder through the valve train.
When this happens, a bluish-white smoke is emitted when the oil burns in the cylinder.
SOLUTION: Continuing to run your Bad Boy with too much oil can cause seal damage, the engine to hydro lock, and a bent piston rod. Correct an engine with too much oil by removing a little oil.
This thick cloud of smoke can plug your air filter causing running issues because your engine isn’t able to get the clean air it needs. Check your air filter and your spark plug, and clean or replace them if needed.
9. Poor Air Circulation Cooling
Your engine needs to be kept cool to prevent it from overheating and losing power. Make sure your engine has good air circulation by removing any grass clippings, dirt, and debris that may be collecting around your engine.
SOLUTION: Remove all the debris that has been collected under your engine shroud.
10. Engine Cooling Fins are Dirty
The cooling fins are essential to circulating air around the engine to keep it cool. Just like you need to remove debris from collecting around your engine so your engine doesn’t overheat and experience a loss of power, the same is true of your cooling fins.
The fins can become plugged with mud and grass clippings inhibiting the amount of air is it able to push to the engine.
SOLUTION: Clean out debris around your cooling fins and replace any broken fins to make sure it is functioning properly.
11. Too Much Load Placed on the Engine
When too much load is put on your engine, you can lose power because the engine has to work harder. You may notice this when your Bad Boy mower loses power when engaging the blades.
Ground Speed is Too Fast for Mowing Conditions
Mowing your lawn at too fast a speed can put extra load on your Bad Boy zero-turn. Slow down the speed to match your mowing conditions. For example, your engine works harder to mow thick lawns over thinly covered lawns.
SOLUTION: You need to operate your zero-turn at a slower speed when mowing thick lawns. Operate your mower slower when on inclines. Mowing inclines makes your engine work harder.
Mowing Wet or Tall Grass
When mowing wet or tall grass, you are making your engine work so much harder than mowing dry grass with a manageable length. Mow your grass when it is dry.
This puts less load on your engine and reduces the number of grass clippings clumping and collecting under your mower deck.
SOLUTION: It is best to mow regularly to prevent your grass from getting excessively tall. When mowing tall grass, adjust your mower deck to its highest setting for the first cutting and then lower the deck for the next cutting.
Avoid mowing in these conditions if possible. If you do need to mow this type of grass, slow down your zero-turn speed to not overwork it.
Grass Buildup Under Your Mower Deck
Keep your mower deck clean so the blades can spin freely. When dirt and grass clippings plug the mower deck, the engine is required to work hard to turn the blades through the buildup with each revolution. The Bad Boy engine can lose power while cutting.
SOLUTION: Regularly scrape your deck to remove debris. Avoid mowing in wet conditions as the grass is more likely to build up under your deck.
Not only does this extra debris under the deck cause your engine to work hard and lose power, but it also causes your Bad Boy mower to give you a bad cut.
Running Dull Zero Turn Mower Blades
What further magnifies the lack of power received when mowing with a clogged mower deck, is mowing with dull mower blades and a clogged mower deck.
SOLUTION: Check your blades and sharpen or replace them if needed. You can find more information on inspecting your blades and the sharpening process here.
Still Experiencing Problems with Your Bad Boy Zero Turn Mower?
Own a lawn mower long enough, you’ll start running into problems with it starting, not continuing to run, smoking, leaking gas, giving a bad cut, vibrating, or another issue.
To help you save time and money, I have put together a guide to help you troubleshoot the next problem that develops on your mower.
You can find this guide at Common Bad Boy Lawn Mower Problems & Solutions.
If you are unsure how to perform diagnostics and repairs on your lawn mower safely, it’s best to have a professional complete the repairs.
This will help you avoid personal injury or additional damage to the mower. Your local Bad Boy lawn mower dealership or lawn mower repair shop will be able to help you solve your problem.