Simplicity Zero-Turn Mower Buyers Guide (Problems & Specs)

Simplicity mowers are some of the best made machines out there. Regardless of how well they are built or maintained though, occasionally, Simplicity zero-turn mowers encounter problems. While you may never come across any problems with your Simplicity zero-turn mower, we have solutions to some of the most common issues.

Routine maintenance can prevent many issues, but occasionally you may experience engine problems, transmission troubles, uneven cuts, engine knocking, black exhaust, or extreme vibration to name a few. These issues could be caused by clogged filters, bad spark plugs, bent or broken blades or pulleys, or other possibilities. With the right knowledge, you can troubleshoot these problems.

Keep reading as we go over all these issues and more. We’ll help you troubleshoot all of these issues and give you practical advice on how to repair them.

Typical Simplicity Zero-Turn Mower Problems & Solutions 

The following list explains the most common problems that may arise from continued, everyday use of your Simplicity mower. Being able to properly troubleshoot your problems will help you repair the mower and save some money. Then you can get out of the garage and back to mowing. 

Problem #1: Engine Won’t Start

Everyone who has owned power equipment has surely experienced this issue a time or two in their lives. When your engine won’t start it can be a result of several possible issues. These can include bad or no fuel, a clogged filter, a dead battery, or fouled spark plugs just to name a few. 

If the battery is working and turning the engine you should start by checking the fuel, and the fuel filter. Is the gas old, or is there water in the tank? If so you should clean it out and replace the old fuel with fresh.

How long was the last time you replaced the fuel filter? If you can’t remember, it could be clogged which will prevent fuel from getting to the cylinder. While you’re checking filters, go ahead and look at the air filter, if it’s clogged, you may not be getting enough air to start the engine.

Next, check the spark plug and wire. Replace them both if you notice excessive wear, a dirty spark plug, cracked wires, or any corrosion on the contacts. 

Be sure to check your oil. Some small engines will not start without proper oil levels. If you notice low oil, check for leaks, and look at the exhaust. Oil levels will go down over time, but if you’re going through a lot of oil you probably have a leak or it’s getting burned in the cylinders.

If the engine doesn’t turn, check the electrical system. Have the battery checked or charged, look for loose or corroded battery cables, or see if the starter needs to be fixed or repaired. Another possible problem is a bad solenoid. If you don’t hear any click or a series of clicks when you try to start your mower, chances are it’s the solenoid.

Problem #2: Hydrostatic Transmission Issues

With hydrostatic transmissions, if air gets in the system, the mower can suffer from cavitation. This can cause the motor to run slowly, or not at all. You’ll have to purge the transmission. 

To do this you need to put jack stands on the back of the mower to lift the tires off the ground, but you’ll need to still keep the mower level or it won’t work. Now make sure the hydraulic fluid is filled according to the manufacturer’s specs. 

Now, disengage the transmission and start the engine. Now increase the throttle slightly to a slow position. Then put the control levers in neutral and disengage the clutch pedal. 

Hydrostatic Transmission

With the clutch disengaged push the throttle levers forward all the way and hold them there for 5 full seconds. When you’ve counted 5 seconds, pull the throttle levers back to a full reverse position and hold them there for another 5 seconds.

You’ll want to repeat this process three times as it should purge any air pockets from the system.

Once that is completed, put the levers back in the neutral position, set the parking brake, and turn off the engine. Add any hydraulic fluid if it’s needed. 

Now, remove the jack stands and put the mower back on solid ground. Start it up again and roll the mower forward slowly about 5 feet, put it in neutral, and then go back about 5 feet. Repeat this step 3 times and check the fluid once again. It should be fixed now, but if it isn’t you’ll need to consult a small engine mechanic.

Problem #3: Uneven Cuts

When your grass is not cut evenly it can make your yard look messy and be very frustrating. Often this is caused by debris or grass clippings trapped in the mower deck, or by dirty, dull blades.

Shut off the engine and safely inspect the bottom of the deck and the mower blades. Remove any debris and clogged grass and make sure your cutting blades are properly sharpened. Rocks, twigs, and even thick grass can dull your blades.

While you’re checking the blades, make sure they aren’t bent. This is another reason your lawn could be cut unevenly. Replace any blades that are bent or damaged. 

Look for an uneven deck and level it back out if that’s the problem. If the deck is damaged or bent, unfortunately, you’ll have to replace it. Once the structural integrity of the metal is compromised, it’s very difficult to get it back. 

One last thing that can cause uneven cuts is mowing too fast. Running over the grass too fast for the blades to cut will cause some pieces of grass to be missed by the blades or only have part cut off. Try slowing down a little bit and see if that helps. 

Problem #4: Engine Starts Hard or Runs Poorly

Most times a hard or poor running engine is a result of a rich fuel mixture. You’ll also smell gas coming from the exhaust because all the fuel isn’t getting burned off and will eventually foul out the spark plug or cause backfiring.

The spark plug could be the culprit here, so check it first. Look for cracks in the porcelain, check the gap, and look to see if the points have worn down. If the spark plug is bad, replace it.

Another problem could be the carburetor. It could be clogged or the valves could be sticking. Try a carburetor cleaner and see if that fixes your problem. If it doesn’t, you may need someone to repair it for you. 

It can be tricky to properly adjust a carburetor if you don’t have experience doing so.

When none of the above parts is the problem, check the fuel pump. It may be dumping too much fuel into the carburetor and needs to be replaced.

Problem #5: Engine Knocking

Engine knocking usually happens when the oil level is too low, too high, or the wrong grade has been added. The wrong amount of oil can cause the engine to work extra hard to push it around and cause a knocking sound.

Check your oil after the engine has been shut off and has had plenty of time to cool off. If you have too much oil, you’ll have to drain some off. 

If you put the wrong grade of oil in, be sure to drain it all out and replace the oil filter and refill it with the recommended manufacturer’s grade.

If your mower is still experiencing a knocking problem even after making sure the oil levels are correct and the right type of oil is in the reservoir, you should have it checked by a mechanic. It could be an internal engine problem that’s making the knocking. 

A valve could be stuck or damaged, or there could be an issue with the camshaft or a piston. All of these problems can be very challenging to fix if you don’t have extensive knowledge about engines, and a plethora of expensive tools. 

Problem #6: Brake Problems

The main reasons you’ll experience brake problems are they were adjusted too tight, or they are worn out and need to be replaced. Brakes on riding mowers may not be high on your list of things to check, but they still need to be replaced just like on your car or truck.

If you have never given thought to your mower’s brakes, go ahead and get them checked, it may be time to replace the tiny brake pads. These pads definitely don’t get the workout your regular vehicle goes through but they still need to be serviced occasionally.

For those of you who are pretty handy, these can be replaced in about an hour or two. If you don’t know how or feel intimidated tackling a task such as this, leave it to the professionals.

Problem #7: Excessive Mower Vibrations

When your mower is vibrating so hard it rattles your teeth, it’s most likely a problem with the mower blades, you’ve got a loose belt or loose mounting bolts somewhere. Turn off the mower and carefully check the mounting bolts on the engine, and the mowing deck.

Tighten any loose bolts you find, and keep an eye on them to make sure they don’t become loose again. When bolts come loose the threads may become damaged. When this happens it’s best to go ahead and replace the bolt so it doesn’t cause further issues.

Belts that continuously slip off may be stretched out and need to be replaced. Then again you could have a bent spindle or pulley. Check all these parts and replace anything that isn’t working perfectly.

The next thing to check is the mower blades. When these get bent, become damaged, or are clogged with debris, they can cause severe vibrations. Replace any blades that show signs of damage, because if you continue to use a damaged blade, you can bend or break other parts on your mower. 

Problem #8: Step Cuts

Steps cuts are a little bit different than uneven cuts. You have an even cut, it’s just that one side ends up higher than the other, giving the appearance of steps. This is usually caused by an uneven deck, but it can happen with a slightly bent blade. 

First off, check the mower deck to make sure it’s aligned properly. Chances are there is a bolt missing or it has fallen off on one side. Realigning the deck will quickly fix the problem and you can now mow your yard evenly.

If your deck is perfectly even, then you have a mowing blade issue. Check to see if one of the blades is bent, if it is, don’t try to shape it back. Mower blades are balanced so that when they spin they don’t shake and vibrate. 

Trying to bend a mower blade back into shape can make the problem worse. Replacing the bad blade, or replacing both of them at the same time will help you avoid any further problems.  

Problem #9: Black Engine Exhaust

Black engine exhaust coming from your Simplicity zero-turn mower is a sign that the fuel mixture is running rich. This could be caused by a clogged air filter or a carburetor issue. Another issue that can be easily overlooked is the choke control.

When getting on and getting off you might have accidentally closed the choke. This restricts airflow and draws in more gasoline which will make your mower belch out black smoke. Just make sure the choke is open, before checking other issues. 

Next check the air filter. When the filter is very dirty or clogged, you’re not getting the proper amount of air into the engine which can cause black smoke. Replace the air filter and see if that helps the problem. 

After replacing the air filter, start the mower and let it run for a few minutes to see if it clears up. If you’re still getting black smoke from the exhaust, you’ll need to check the carburetor. It could be clogged or dirty. 

Sometimes fuel and debris can get into the carburetor and keep it from working efficiently. A little bit of carburetor and fuel system cleaner should have it running properly once again. But if that doesn’t fix the black smoke, you should take it to a mechanic. 

Problem # 10: Mower Belt Slippage

Anyone who has owned a riding mower for more than one season has inevitably experienced the mower belt slipping off or getting too loose to turn the blades properly. Mower belts aren’t meant to last forever. They stretch, crack, fray, break, and can fly off at high speeds.

It should be common practice to check your belts each time before you start the mower. Check for any obstructions such as grass, rocks, or twigs in the way. Look for looseness, cracks, fraying, or any other damage to the belt, and replace it whenever you notice any of these issues.

If you have recently replaced the belt and it continues to slip off, then you’ll need to check the pulleys and tensioner. Pulleys can become bent, or get damaged which can cause the belt to slip off, especially when you initially engage the blades. 

Inspect the grooves of the pulleys to make sure they aren’t damaged. Then check that they aren’t loose and wobbly, or bent out of shape. If any of these issues are apparent, you’ll need to replace them before engaging the blades again.

After you have checked the pulleys and found that they are all in perfect working order, check the tensioner pulley. These are attached to arms or springs that help keep the belt tight, but not too tight. If it’s loose and flopping around, then your belt isn’t able to work properly.

You may have to replace the pulley or the whole assembly to keep the belt from slipping off again.

Another thing to be on the lookout for is plastic pulleys. Some manufacturers have been installing plastic pulleys on belt drives to make the mowers lighter, and to save money. The problem is plastic wears out much faster and is not as strong as metal. 

The plastic pulley may appear to be in good shape, but it can be worn down just enough so that it isn’t able to hold the belt tightly as it should. If you see a plastic pulley on your mower’s deck, you may want to consider replacing it, even if it’s not causing you any issues at the moment.


Simplicity zero-turn mowers don’t often have problems because they are exceptionally built machines, but when they do, having the knowledge to troubleshoot them is priceless. With this knowledge, you may be able to quickly and efficiently repair the problem yourself. 
You could save plenty of time and a lot of money by doing these simple repairs yourself. But of course, if you are uncomfortable tackling these problems yourself, please seek a professional to repair your mower. We hope this has helped you fix the issues you have been experiencing.

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