9 Common Riding Lawn Mower Problems & Solutions
It doesn’t matter what brand of riding mower you bought, when you own it long enough, you will run into problems with it.
That is why I put together this guide to help you identify the causes of your problem. Follow the links in each section for more in-depth information on the problems you are experiencing.
The most common riding lawn mower problems are:
- Riding mower won’t start
- Riding mower dies while mowing
- Riding mower is smoking
- Riding mower has a weak hydrostatic transmission
- Riding mower won’t drive straight or steer correctly
- Riding mower won’t move
- Riding mower is shaking or vibrating
- Riding mower is cutting uneven
- Riding mower is leaking fuel
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Follow all safety instructions provided in your equipment operator’s manual prior to 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.
Table of Contents
10 Common Riding Lawn Mower Problems & Solutions
Riding Lawn Mower Won’t Start
A riding lawn mower can fail to start when you have a fuel or air restriction due to a plugged air filter, clogging of the fuel system, or failing fuel components.
You may also experience bad electrical problems including a dead battery, faulty charging system, dirty spark plug, bad switches, or bad connections that can prevent your riding mower from starting.
Detailed information can be found at:
Reasons Your Riding Mower Won’t Start
| Cause | Reason for Problem | Solution |
| No gas in the fuel tank | Fuel tank is empty | Fill with fresh fuel |
| Bad or old fuel | Fuel breaks down overtime making your fuel less efficient and prone to clogging the fuel system | Drain the fuel tank and fill it with fresh fuel. Use a fuel additive like Sea Foam to stabilize the fuel and assist with cleaning the fuel system. Use the right fuel. |
| Faulty or clogged fuel cap | The vent in the cap can get clogged causing your tank to form a vacuum restricting fuel flow | Use a thin piece of wire to try to clear the clogged vent. Replace the cap if needed. |
| Bad spark plug | Excessively dirty or broken spark plug; bad connection; not gapped correctly | Replace with a new spark plug, secure connections, and ensure it is gapped to manufacturer specifications |
| Plugged air filter | Dirt and grass can plug the air filter preventing airflow | Remove the filter and clean it. Replace the filter if it is in bad condition. |
| Plugged fuel filter | A dirty fuel filter will restrict fuel flow | Replace the fuel filter |
| Bad fuel pump | A failed or leaking fuel pump will no longer create the pressure needed to pump fuel | Replace the fuel pump |
| Blocked fuel lines | Bad fuel deposits and dirt can build up and clog the fuel lines preventing the engine from getting the required fuel | Use a carb cleaner and compressed air to clear the clog out of the fuel line. Replace the line if necessary. |
| Dirty carburetor | The carburetor can become dirty and clogged due to bad fuel and ethanol deposits preventing fuel flow | Clean the components making up the carburetor. Replace if needed. |
| Bad battery or loose & dirty terminals | A dead battery, loose cables, or corroded terminals can cause starting problems | Charge your battery and replace if it won’t hold a charge. Make sure your cables are tight and clean the corrosion from terminals. |
| Bad safety switch | Safety switches are a safety measure that exists to prevent your mower from starting in certain situations. When a switch fails, your mower may not start. | Test and replace faulty safety switch |
| Bad ignition switch or coil | Your mower will not start when either the ignition switch or coil is bad | Test and replace a bad switch |
| Broken recoil | A pull start mower may have a damaged or broken recoil preventing the recoil to initiate starting your engine | Check the recoil to see if it can be restrung or if broken parts, like the pulley, can be replaced. Replace the recoil assembly if needed. |
Riding Lawn Mower Starts Then Dies
You’re mowing the lawn when your riding mower suddenly dies. Being stuck in the middle of your yard with a mower that is dead is frustrating. A riding mower may die when old fuel is used causing clogging in the fuel components or engine damage.
Your engine needs to be kept cool to prevent damage or it will die. A plugged air filter, wrong engine oil, incorrect oil level, and plugged mower deck can contribute to your engine overheating and shutting down.
A riding mower can also die after its been running from a faulty charging system that isn’t able to keep your battery charged, a dirty spark plug, bad ignition coil.
Detailed information can be found at:
Your Riding Lawn Mower Starts Then Dies
| Cause | Reason for Problem | Solution |
| Bad fuel | Fuel breaks down overtime making your fuel less efficient and prone to clogging the fuel system and engine damage | Drain the fuel tank and fill it with fresh fuel. Use a fuel additive like Sea Foam to stabilize the fuel and assist with cleaning the fuel system |
| Plugged air filter | Dirt and grass can plug the air filter preventing airflow | Remove the filter and clean it. Replace the filter if it is in bad condition. |
| Dirty or broken cooling fins | Cooling fins get packed with dirt, oil, and grass not allowing air to effectively cool the engine block | Replace broken fins and clean the cooling fins. |
| Clogged fuel lines or filter | Bad fuel deposits and dirt can build up and clog the fuel lines preventing the engine from getting the required fuel | Use a carb cleaner and compressed air to clear the clog out of the fuel line. Replace a plugged fuel filter. |
| Dirty carburetor | The carburetor can become dirty and clogged due to bad fuel and ethanol deposits preventing fuel flow | Clean all components making up the carburetor. Replace if needed. |
| Too Much Engine Oil | Too much engine oil increases pressure in the crankcase causing it to overheat and die | Correct your engine oil level by removing a little oil |
| Bad Spark Plug | A dirty or damaged spark plug causes the plug to foul out and cause intermittent running problems. | Clean or replace spark plugs if needed. Ensure spark plug wires are securely attached and the plug is gapped correctly. |
| Faulty Ignition Coil | Windings on the coil can separate and short out a bad ignition coil | Check for a break in the continuity using an ohm meter and replace is found bad |
| Choke is in the Wrong Position | A choke is used for cold starts. The choke can cause your engine to shut off when it continues to restrict airflow after the engine warms. | Make sure the choke is in the correct position |
| Bad Gas Cap | Gas caps have vents for air to pass through. When the vents get plugged, the fuel tank will cause fuel restrictions. | Replace a fuel cap that no longer vents |
| Clogged Mower Deck | A clogged mower deck causes a strain on the engine causing it to work hard and possibly shut down | Periodically scrape your mower deck to keep it clean |
Riding Lawn Mower is Smoking
Smoke rolling out of your mower can be very alarming. This can sometimes be fixed by replacing your air filter, correcting your engine oil level, or replacing a gasket causing an oil leak.
Other times, it is not so simple of a fix. The engine may have an internal problem that will need to have tests performed by a small engine mechanic to narrow down the problem.
Detailed information can be found at:
This is Why Your Riding Mower is Smoking
| Cause | Reason for Problem | Solution |
| Plugged air filter | Dirt and grass can plug the air filter preventing airflow | Remove the filter and clean it. Replace the filter if it is in bad condition. |
| Too much oil in the crankcase | Excessive oil can cause pressure to build in the engine allowing oil to get into the cylinder through the valve train | Drain a little engine oil until it is at the manufacturer’s recommended oil level. |
| Engine oil level is too low | Lack of oil can increase friction in your engine causing extreme heat. | Bring to a small engine repair shop to inspect engine damage. You can try adding oil, but it is often too late to have this fix your engine problem. |
| Internal problems including the piston ring, valve train or engine gasket | Internal engine problems can have a detrimental effect on your mower if they are not caught soon enough and fixed. | Have your mower diagnosed by your local small engine repair shop. |
Riding Lawn Mower Hydrostatic Transmission is Weak
| Cause | Reason for Problem | Solution |
| Bad drive belt | A bad drive belt can cause your pump not to work efficiently | Replace a frayed, cracked, or worn belt |
| Bad tensioner pulley | When a tensioner pulley fails, it fails to keep tension on the drive belt | Replace the pulley and grease the tensioner arm |
| Low or old hydraulic oil | Low or old hydraulic oil can fail to lubricate the hydraulic system causing your hydraulic system to seem weak | Change your hydraulic oil at regular intervals as recommended by the riding mower manufacturer. Check your hydraulic oil periodically to ensure your hydraulic fluid is full. (Some transmission systems are sealed and they can’t be serviced. If you are having trouble with a sealed system, see your dealer). |
Riding Lawn Mower Won’t Drive Straight or Steer Correctly
It can get frustrating when you are always having to adjust the operation of your mower because it is pulling to the right or left. Here is a list of items to check on a riding lawn mower to make the necessary corrections to get your mower to drive straight.
| Cause | Reason for Problem | Solution |
| Incorrect tire pressure | Unequal tire pressure can cause your mower to pull to one side. | Check tire pressures and keep them filled to the manufacturer’s spec. Tires on each side of your mower require equal pressure. |
| Worn or loose steering components in riding mower | Worn bushings, washers, and gears can cause your mower to not steer one way or the other | Inspect and replace the parts that failed on your steering system |
Riding Lawn Mower Won’t Move
A riding lawn mower may not move when the drive levers on hydrostatic mowers are not in the correct operating position. A bad tensioner, missing idler arms spring and worn belt can also affect a riding mower’s movement.
Running old hydraulic fluid or having air in the system can cause your mower to move slowly or not at all.
Detailed information can be found at:
9 Reasons Your Mower Won’t Move or Go Forward
| Cause | Reason for Problem | Solution |
| Drive release lever in the wrong position | The drive release lever allows hydrostatic mowers to roll freely | The drive release lever must be in the operating position. |
| Missing key in the axle | Your riding mower may have a small key in the axle that may have fallen out of place | Replace the key in the axle |
| Bad tensioner pulley | The bearing in the tensioner pulley can fail | Replace the tensioner pulley |
| Missing idler arm spring | If the idler arm spring breaks or goes missing, it can no longer place tension on the drive belt | Replace the broken or missing spring |
| Worn drive belt | A worn drive belt will slip on the pulley and cause your mower to run sluggishly. The belt can break or fall off the pulley and your mower will no longer move. | Replace a worn drive belt |
| Low or old hydraulic oil | Low or old hydraulic oil can fail to lubricate the hydraulic system causing your hydraulic system to seem weak | Change your hydraulic oil at regular intervals as recommended by your riding mower manufacturer. Check your hydraulic oil periodically to ensure your hydraulic fluid is full. (Some transmission systems are sealed and they can’t be serviced. If you are having trouble with a sealed system, see your dealer). |
| Hot hydraulic fluid | Hot hydraulic fluid can be a sign of damage to your hydrostatic transmission system | Let your hydraulic oil cool. If you find your mower runs fine when it is cold, but becomes weak when the hydraulic system gets hot, have your mower checked at your local manufacturer dealership. |
| Air in the hydraulic system | Air must be bled from the hydraulic system after changing your hydraulic fluid or the mower will not be able to move at normal speeds | Follow your mower manufacturer’s procedures for changing the hydraulic fluid and bleeding air from the system in your owner’s manual. |
Riding Lawn Mower is Vibrating
When your lawn mower begins vibrating and shaking more than normal, it’s time to look over your mower carefully for any extra debris caught in your mower. You would be surprised at some of the little things I have found stuck in a mower that cause a significant vibration.
A riding mower vibration can be caused by running unbalanced or damaged mower blades; loose and missing hardware; bearing failure in the pulleys and spindle housings; and a bad clutch.
Detailed information can be found at:
Solved! Your Riding Lawn Mower Vibration
| Cause | Reason for Problem | Solution |
| Loose or missing engine mounting bolts | Engine bolts are used to reduce the vibration of the mower when the engine is running | Secure engine bolts and replace any missing bolts |
| Clutch is bad | When there is bearing failure and it falls out of the clutch it can cause vibration. A manual engagement clutch can have a bushing and linkages that can fail. | Replace the clutch |
| Unbalanced or damaged mower blades | Damaged and unbalanced blades can send a vibration through your mower. Blades must be balanced before installing | Replace any damaged blades and make sure they are balanced. |
| Material wrapped around the blade spindle | Foreign materials like string or long weeds can get wrapped around your blade shaft causing vibration | Remove all debris and items wrapped around the blade shaft. Check for spindle damage. |
| Bad spindle housing bearings | Vibration can be caused by a bad bearing in the spindle housing. | Replace the bearing in the spindle housing or replace the whole spindle housing assembly |
| Worn pulleys or deck belt | Check deck belt and pulleys for wearing of the belt and bearing failure in the pulleys | Replace any damaged or worn belts and pulleys |
| Debris lodged in mower | The smallest little things can cause a riding mower to excessively vibrate. Check over your mower for debris stuck in the deck or mower. Don’t overlook the small stuff. | Check over your mower deck and mower for any place small items can be stuck in your mower. Remove these foreign materials. |
Riding Lawn Mower Has a Bad or Uneven Cut
Detailed information can be found at:
Reasons Your Riding Mower is Cutting Uneven
| Worn mower blade | Uneven tire pressures | Engine speed is too low |
| Bent mower blade | Unleveled mower deck | Ground speed is too fast |
| Blade installed wrong | Bent blade spindle or spindle bearing | Damaged deck shell |
| Clogged Mower Deck | Worn deck pulleys or belt | Operator error |
Riding Lawn Mower is Leaking Gas
Fuel will evaporate making it increasingly difficult to find a lawn mower fuel leak on your mower if you don’t physically see it dripping or forming a wet spot.
A riding mower can begin leaking gas from old, dry, or degraded fuel components including the fuel filter, carburetor, fuel pump, and fuel lines. It can also be from a failing seal in a fuel cap.
Detailed information can be found at:
Why Your Riding Mower is Leaking Gas
| Cause | Reason for Problem | Solution |
| Dirty of Failed Carburetor | The carburetor can collect a buildup of substances remaining from old gas that can cause blockages or parts failures | Clean the carburetor and replace any damaged parts |
| Old Fuel Filter | Filter can become plugged | Replace fuel filter |
| Bad Fuel Pump | Pump can wear and deteriorate over time and may begin leaking at the seams | Replace the fuel pump |
| Bad Fuel Tank | A metal tank can develop a rust hole. A poly tank can leak at the seams of the tank. | Replace the fuel tank. Sometimes, a rust hole can be repaired if you can no longer find a replacement tank. |
| Bad Fuel Shut-Off Valve | Metal and plastic shut-off valves are prone to leaking | Replace the shut-off valve |
| Cracked Fuel Lines | Rubber fuel lines become dry and cracked causing gas to leak | Replace the fuel lines |
| Bad Seal in the Gas Cap | The gas cap seal can fail and no longer seal allowing gas to splash out of the fuel tank around the gas cap | Replace the gas cap |
Additional Guides for Your Riding Lawn Mower
Check out these articles for additional help with your riding mower:
How to Service Your Riding Mower: Step-By-Step
Your Riding Mower Isn’t Getting Fuel
