You made a significant investment to get the quality cut provided by your SCAG mower. You love the cut your mower provides until you start noticing the quality of the cut has changed and it doesn’t look very good. Luckily, this is something that can be easily fixed most of the time.
A SCAG lawn mower cuts bad or uneven when the tire pressure is low; the mower blade is bent, worn, dull, or unbalanced; the deck belt is worn; the spindle, spindle bearing, or pulley is bad; the mower deck is plugged; the ground speed is too fast, or the engine speed is too low.
Before working on your SCAG mower, make sure you have removed the spark plug boot and wait for all parts to stop moving. Follow the safety precautions in your operator’s manual before performing any diagnostic procedures or 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.
Reasons Your SCAG Lawn Mower is Cutting Uneven
1. Low Tire Pressure
Before you check anything on your SCAG mower, you need to check the tire pressures. Don’t skip this step or you may end up making adjustments to your mower that are not needed.
This will create more work when you have to reverse these prior adjustments once you find a low tire.
The pressures in both drive tires should be equal to each other. When one tire is lower in pressure than the other, the mower deck will no longer sit level with the ground.
This can cause your mower to give you an uneven cut where the grass cut on one side of the deck is longer than the grass cut on the other side. Use a tire pressure gauge and check the tire pressure.
Refer to your operator’s manual for the tire pressure specification recommended by SCAG. Make the necessary tire pressure changes.
2. Worn or Dull SCAG
Sharp mower blades that are in good condition play a significant part in maintaining a quality precise cut. Dull or worn blades can be the reason why your SCAG is giving you a bad cut.
Worn SCAG Mower Blades
Blades that are not regularly replaced can become worn. Dirt and debris get sucked into the deck wearing the blade. Over time, the blade can become so worn that the ends of the blade become rounded and the blade sail becomes thin.
Rounded blade ends can leave uncut strips of grass. A worn blade sail will restrict the amount of airflow that is created under the deck to lift the grass to achieve that nice cut.
Without good airflow and suction under the deck, you will get an uneven cut.
When you find the blade tips are rounded or the sail is thinner than the center of the blade, it’s time to replace your mower blades with a new set.
Dull SCAG Mower Blades
The blade edges naturally become dull with use. There is no way to prevent this. Dull blades will end up beating up your grass instead of precisely cutting it leaving it with a brownish appearance a couple of days later.
When you notice a brownish appearance to your lawn, it may be a sign your SCAG mower is bruising and tearing the grass instead of giving it a good cut with a sharp blade.
Confirm this by grabbing a handful of grass and looking at the ends to see if they are torn and brown.
I recommend starting each season out with a new set of blades and sharpening them a couple of times during the mowing season.
If you use your mower more than the average homeowner or you are mowing in very dusty conditions, you will have to check and sharpen your blades more frequently.
3. Bent Mower Blade
You hear a loud clunk or grinding noise and know you hit something with your mower. A blade spinning at high rates can bend when it impacts a solid object.
Not only can the blade bend, but an impact can also damage the spindle and spindle bearing.
Even if you can’t remember hitting something significant, you may have had an impact that could have slightly bent the blade. No matter how severe the bend, a bent blade can give you an uneven bad cut.
To prevent impacting hard objects, take a few minutes to walk your lawn and look for objects that could potentially damage a mower blade. These are items like tree roots, rocks, and toys.
Remove the items that you are able to and mow around items that are not easily removable like tree roots.
There are a couple of different ways you can check for a bent blade. Before you remove the mower blade, it’s a good idea to quickly check the condition of the spindle and spindle bearing. Refer to the section on the spindle housing below.
Check for a bent blade with the blade on your SCAG lawn mower
With your mower parked on a flat level surface. Measure the blade end from the ground to the blade. Record the measurement.
Rotate the blade 180 degrees and measure from the same spot in the ground to the blade end. Record the measurement.
If you find your mower blade has more than a 1/8” difference between the two measurements, your blade is bent and should not be reused.
Check for a bent blade with the blade off your SCAG lawn mower
For this step, have a good blade you can compare each used blade against.
Place the used blade on top of your good blade and look for gaps or bend in the blade that shouldn’t be there. Do not reuse a blade that does not sit flat against the good blade.
NEVER ATTEMPT TO STRAIGHTEN & REUSE A BENT MOWER BLADE. Doing so can put you and others in an extremely dangerous position.
Bending a mower blade back into position will compromise the metal, making it weak and more likely to crack. A blade spinning at very high speeds that breaks off puts people in the area at risk of injury.
4. Unbalanced Mower Blade
An unbalanced blade is a blade where one side of the blade is heavier than the other. This can happen from uneven wearing from normal use.
It can also become unbalanced when more metal is shaved from one side of the blade while sharpening it.
An unbalanced blade can cause your blade to wobble when it rotates under the mower deck. At very high speeds, the blade can cause significant vibration and spindle bearing damage.
Check the balance of a sharpened SCAG mower blade before installing it on your mower. A blade balancer is designed to do just this.
This is an inexpensive tool that will help ensure your blade is properly balanced. It can save you from causing additional damage to the mower.
If you don’t have a blade balancer, you can try this alternative method:
- Place a nail in the wall with the nail head about 1 inch away from the wall.
- Place the center of the blade onto the nail.
- A balanced blade should sit level and parallel to the ground. If one side sits lower, you must shave a little metal off that end until the blade sits level on the nail.
5. Damaged Spindle or Bad Spindle Housing Bearing
Your blade will wobble when the spindle or spindle bearing is damaged. This can cause a significant vibration at high speeds and provide you with an uneven cut.
It’s best to check for a problem in the spindle housing while your blades are still attached. With a heavy pair of gloves, grab a hold of each end of a mower blade and rock it up and down.
If the spindle and bearing are good, you shouldn’t feel any movement.
If you do feel movement or hear a knocking sound, you will need to remove the blade and spindle housing and check the spindle and bearing for damage. Replace any damaged parts you find.
6. Clogged Mower Deck
Earlier, I mentioned the importance of the sail on your mower blade. It is used to create air movement under the deck to form a suction. This suction lifts the grass so it stands tall while the blade passes by to cut it.
The deck is designed to maximize the space under the deck for optimal air movement so you can get that good cut.
When the mower deck is packed full of grass clippings and yard debris, it reduces the amount of space available for good airflow and suction.
A plugged mower deck will not only give you an uneven cut, it will also cause strain on your mower’s engine.
Keep your mower deck clean and free of debris. Scrape the deck regularly to prevent excessive buildup. To minimize buildup under the deck, avoid mowing in wet conditions. Wet grass will clump and stick to the underside of your deck.
You can attempt to use a spray to reduce the amount of buildup under the deck. Just understand, no spray is going to prevent all debris from sticking. It will only minimize it.
7. Mower Deck is Not Level
A deck that is not level can give you an uneven cut. When one side of your deck sits lower than the other, the mower may give you a stair-step kind of cut.
Because adjustment procedures for leveling your SCAG mower deck vary by model, refer to your operator’s manual for leveling procedures.
Makes sure the deck is level from side-to-side. Then check the rake (front to rear) measurements and compare them to the specifications required for your model. The front of the deck does sit slightly lower than the rear.
8. Bad Deck Belt
A SCAG mower deck belt that is worn will fail to grip your pulleys and turn your blades at high speeds. A reduced blade tip speed will compromise your cut quality. Inspect your belt and look for signs of wear.
This includes a glazed shiny appearance or cracks in the belt. A stretched belt that doesn’t sit tight to the pulleys or one that sits deep in the pulleys is also a sign of a worn belt. You must replace a worn belt with a new one.
9. Bad Pulley Bearing
The bearings in your pulleys on the SCAG lawn mower can become bad. This can cause your pulleys to not sit flat and securely on the deck.
There may be some vertical movement in the pulley causing one side of the pulley to sit higher off the deck than the other side.
To check for a bad pulley bearing, slowly spin each pulley by hand. Feel for a restriction and listen for bearing noise. When you experience either of these symptoms, replace your pulley.
10. SCAG Lawn Mower’s Low Engine Speed
When you engage your mower deck, you must have your SCAG mower running at full throttle.
You need the engine speed to be at its highest to be able to send enough power to the mower deck to spin your blades and give your lawn a good cut.
You may be running your SCAG lawn mower and realize your engine is no longer giving you the power required to cut your lawn.
If this is happening to you, have a small engine mechanic check and perform tests on your engine to identify any potential problems causing your engine to not give the power you need.
11. Too Fast a Ground Speed
Your engine can get overloaded when mowing at fast speeds causing your SCAG mower to give you a bad cut. Just like I mentioned above, an engine that doesn’t give you enough power can result in a bad mower cut.
Know your mowing conditions and adjust your speeds accordingly to not bog down your engine. When mowing tall, wet, or thick grass, you must operate at slower speeds.
Additionally, slow down when operating on hills. Mowing at too fast of speed can cause your mower to not cut all the grass or end up pushing it over instead of cutting it.
12. Incorrect Overlapping of Paths
Overlap your mowing paths to not leave strips of grass between each pass. If you have a new mower, this can take some time to get right.
You want to space your paths so you can save time and not keep mowing over the same section twice. It takes a little practice with your mower to get it just right.
13. Damaged Mower Deck
If you accidentally run into a fence, tree, pole, or another item, you can damage the deck shell. This can give your mower an uneven cut if it is not corrected.
If you are unable to fix your deck shell, you will have to replace it with a new shell.
If you need a deck shell replacement, I recommend contacting your SCAG mower dealership and getting a quote for a replacement deck along with the labor charge to swap all the components over to a new deck shell.
Compare this with a complete deck replacement. You may be surprised to find there isn’t a large price difference. With these two price quotes, you can make the right decision for you based on price and your SCAG mower’s condition.