A Big Dog zero turn has a bad or uneven cut due to low tire pressure, unlevel deck, spindle damage, worn pully or spindle bearing, dull or damaged blades, worn deck belt, or a plugged mower deck.
Keep reading for additional items that may cause a bad cut including operating the mower wrong.
Refer to your Big Dog operator’s manual for safety precautions that need to be taken when working on your mower deck. This includes removing the ignition key and spark plug wires.
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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 Big Dog Mower is Cutting Uneven
1. Low Tire Pressure
Owners often overlook their tires when they have an uneven cutting problem. Before checking any other step for an uneven cut, check your tire pressure.
Low tire pressures will cause your deck to sit unleveled and give you an uneven cut.
Make sure the tire pressures are correct and the same on the right and left-hand sides of the mower. Skipping this step may cause you to make unnecessary adjustments to your mower deck that will have to be reversed once you realize your tire pressures are incorrect.
2. Worn or Dull Blade
It’s normal for your Big Dog mower blade to become worn and dull after extended periods of use. How quickly this happens depends on the mowing conditions.
Lawns that allow more dirt to be sucked under the mower deck will wear blades quicker than those that allow less dirt.
For example, thin grass-covered lawns expose the mower deck to more dirt than thick grass-covered lawns. There’s not too much you can do about the coverage of your lawn other than wait for the grass to fill in and become a thick blanket of grass.
You may notice the grass tips turn brown a couple of days after you mow your lawn. This is a sign your mower blades are dull.
Additionally, blades that are extremely worn and rounded at the ends can leave strips of grass between the blade ends uncut.
It’s important to check your Big Dog mower blades regularly to sharpen or replace them when needed.
When inspecting the edges of your blades for wear, also check the sail on your blades for wear. This is the high side of the blade. If it is thinner than the center of the blade, you can experience a bad cut.
This is because the sail of the blade creates air movement under the deck when rotating at high speeds.
This air movement along with the area under the deck creates a suction that stands the grass tall. The blade then passes over the grass to give it a nice even cut.
3. Gouged or Bent Blade
An uneven cut can be the result of a bent mower blade. A blade can bend when it hits a solid or stationary object like a tree root or rock. Take time to look at the blades for damage.
If you find the blades have chips or gouges in the blade edge, you can remove small nicks by sharpening your blades. You may have to replace the blades with new blades when the gouges are too large to remove.
Continue to check for a bent blade. When the bend isn’t significant and hard to visually notice it, follow one of these methods to determine whether the Big Dog blade is bent:
Without removing your Big Dog mower blade:
- Park your mower on flat ground
- Remove the key and spark plug boot to prevent the mower from turning on.
- Take the measurement from the tip of one end of the blade to the ground. Record the measurement.
- Turn the blade 180 degrees to measure the opposite end of the blade. Record the measurement.
- If there is over and 1/8″ variance from one blade end to the other blade end, replace with a new blade.
- Repeat this step with each blade on your Big Dog mower.
By removing your Big Dog mower blade:
- Park your mower on flat ground
- Remove the key and spark plug boot to prevent the mower from turning on.
- Gain access to the underside of your deck. Remove the mower blade.
- Lay the old blade on top of a new blade. If the blades don’t fit together and leave any gaps, you must install a new mower blade.
If you find a bend, you will need to check the spindle bearing for damage. The bearing can fail when there is a significant impact on the blade.
Never attempt to straighten a mower blade. Doing so will compromise the metal and make it more prone to crack. A cracked mower blade is hazardous when spinning at high rates of speed.
4. Blades are Installed Incorrectly
The high side of the blade, known as the sail or fin, must point up when installed on your Big Dog mower deck.
Installing your blades upside down can not only hit the ground and tear up your grass, but it can also damage the blade spindle and spindle bearing.
Make sure your blades are balanced before you install them. Unbalanced blades can cause an uneven cut and send a vibration through your mower.
5. Mower Deck is Plugged with Debris
Big Dog mower decks are designed to use the area under the mower deck, the baffles, and the air movement from the mower blades to create a suction. This suction stands the grass tall while the blade cuts the grass for an even cut.
When the deck is plugged, it can’t create the suction needed for a quality cut. You must check and scrape your deck periodically.
You’ll have to scrape it more often when cutting wet grass. Wet grass tends to stick to the mower deck and leave clumps in your yard.
Some Big Dog mower owners choose to use a silicone spray meant for mower decks to prevent some of the debris from sticking to your deck. This spray helps, but it will not prevent all of the grass from sticking.
6. Bent Blade Spindle
Check the blade spindles for a bent spindle or a damaged bearing. Again, make sure your spark plug boot(s) is removed and the ignition key is removed for safety.
With a pair of heavy gloves, grab a hold of each end of your mower blade. Rock the blade up and down and check for movement.
If you feel movement or hear a knock, you most likely have a bad bearing in the spindle housing or a bent spindle. You will need to repair or replace any damaged parts.
7. Bad Mower Deck Belt or Pulleys
Turn each pulley on the deck slowly to see if you can feel any resistance or hear any noise. Replace any pulleys that don’t rotate smoothly or you hear a noise coming from the bearing.
Make sure your belt is in good condition without cracks and wear. The belt must run securely around the pulleys.
8. Engine Speed is Too Low or Ground Speed is Too Fast
You must run your engine at full throttle whenever you have your mower deck engaged. You must also adjust your ground speed when mowing thick, tall, or wet grass.
Cutting grass in these types of conditions puts extra work on your engine so slowing your groundspeed will reduce the load on the engine.
When your engine and deck are unable to handle the load on the mower, it may not provide a good cut. Mowing too fast can also cause your mower to not be able to create a good suction and end up pushing over some grass.
9. Incorrect Overlapping Path
Sometimes the cutting problem is the fault of the operator. When mowing stripes in your lawn, you need to overlap each pass so you don’t miss any sections of grass and leave strips of grass in the lawn.
10. Deck Shell is Damaged
A deck shell can get tweaked by running your mower into objects like trees, rocks, and other hard surfaces.
The deck shell is formed to create a suction to give you a good cut. If the deck has been damaged, your cut could also be compromised.
11. Your Lawn is Uneven
When your lawn is uneven and bumpy, your mower deck can scalp the lawn. For a nice-looking cut, it will help to roll your lawn to smooth it out.