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9 Reasons a Spartan Lawn Mower is Vibrating & Shaking

Your mower naturally vibrates from the engine. Unless you have a perfectly flat lawn, you’ll also experience some extra bounce from mowing an uneven lawn. Even though these items will cause some normal vibration in the mower, there are other items that can cause extreme vibration.

A Spartan lawn mower will vibrate and shake due to worn engine mounting bolts, bad ball bearing in the clutch, or debris lodged in the mower. Unbalanced mower blades; bad bearings in the spindle housing or pulleys; or a worn belt, idler bracket or spring can also cause a vibration in a Spartan mower.

Remove the spark plug wire and ignition key before performing any repairs. Take extreme caution when working with your mower deck. You can find all safety procedures outlined in your Spartan operators manual.

Spartan mower deck

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Follow all safety instructions provided in your equipment operators manual prior to diagnosing, repairing or operating. Consult a professional if you don’t have the skills, knowledge or are not in the condition to perform the repair safely.

Troubleshoot: Spartan Mower Vibration

  • Check the engine bolts for wear
  • Check the clutch for a bad ball bearing
  • Check for material wrapped around the blade shaft
  • Check the spindle housings for wearing or damage
  • Check the blade balance
  • Check for worn bearings in the pulleys
  • Check for a worn or stretch belt
  • Check the idler bracket and spring
  • Look for debris lodged in the mower

Reasons Why Your Spartan Lawn Mower is Vibrating

Worn or Missing Engine Mounting Bolts on a Spartan Mower

You’re always going to feel some vibration from the engine, but much of the engine vibration is absorbed by the engine mounting bolts. They are often referred to as motor mounts.

Look at the bolts mounted under the engine to ensure they are in good condition and securely in place. If you find bolts that are worn, broke or missing, you must replace them.

Failing Clutch on a Spartan Mower Causes Vibration

The ball bearing may fail on an electric clutch causing your mower to shake. Replace the clutch when it is found to be the problem of your vibration.

Incorrect or Unbalanced Spartan Mower Blades Causes Vibration

Installing the wrong blades or unbalanced blades on your Spartan mower can cause a vibration.

Wrong size Spartan mower blades:

I always choose to use OEM (Original Equipment Manufacturer) blades to ensure I am using the correct quality blades designed for my zero turn. Using the wrong blades can cause vibration and damage to the mower.

If you choose to use an aftermarket blade, not an OEM blade, you must make sure the blade length and center hole size is correct. Keep in mind, just because you have these two dimensions correct, doesn’t mean the blade will fit right.

When choosing an aftermarket blade, lay it on top of an OEM blade to make sure it is an exact match. A blade that is a little different may cause the blade to not sit securely on the spindle, hit the mower deck shell, create a vibration and not provide a good cut.

Unbalanced Spartan mower blades:

Blades can become unbalanced and no longer spin evenly under the deck. They will begin to wobble as they spin. At very high speeds, you will feel a significant vibration.

An unbalanced blade is a blade that is heavier on one end of the blade than the other. There are a couple different reasons a mower blade to become unbalanced.

  • Normal Use: Dirt rotating under the mower deck can wear the blades unevenly.
  • Blade Sharpening: Too much metal is removed from one end of the blade than the other.

Make sure your Spartan blades are balanced using a blade balancer before you install blades on your mower. Find out more about sharpening and balancing your blades here.

Material Wrapped Around a Spartan Mower Blade Spindle Causes Vibration

You don’t always see everything you mow over. You might not see wire or string in the grass that can wrap around the blade spindle causing the mower to shake.

Inspect the spindle and remove any items that are wrapped around it. Once this is done, check your spindle and spindle housing for further damage.

Damaged Spindle Housing Components on a Spartan Mower Causes Vibration

You may have impacted an object that bent the spindle or the bearings could have worn in the spindle housing causing a vibration when you engage the blades.

Before you check the housing for damage, confirm the spark plug wire is removed and put on a good pair of work gloves to protect your hands from sharp edges. Grab a hold of each end of the mower blade and rock it up and down.

You blade should feel secure and shouldn’t have a lot of movement. If you feel movement and possibly hear a knocking sound from the excess movement, remove the mower blade and spindle housing. Inspect for bearing or spindle damage and repair.

Worn Mower Deck Belt on a Spartan Mower Causes Vibration

When a mower deck is worn and stretched leaving some slack, the belt will not sit securely around the pulleys. This extra slack as the belt moves around the deck pulleys can cause your Spartan mower deck to vibrate.

Replace a worn belt if you find it is stretched, cracked or has a glazed appearance. If the belt appears in good condition, make sure it is routed around the pulleys correctly and the tension is adjusted to remove extra slack.

Bad Pulley Bearings on a Spartan Mower Causes Vibration

Bearings in the pulleys can fail over time which can cause them to not sit securely flat and parallel to the mower deck. When the pulleys have some movement to them and not longer sit parallel, there will be some vibration due to the belt running along these unstable pulleys.

Check each pulley to make sure it is securely attached to the deck and doesn’t have a wobble to it. You don’t want a lot of movement in the pulley where one side of the pulley sits higher off the deck than the other. When this happens, you most likely have a bad bearing in the pulley.

Find a failing bearing by slowly rotating each pulley by hand. Feel for a restriction and listen for a bearing noise. If you experience either of these, your bearing must be replace.

Worn Idler Bracket & Spring on a Spartan Mower Causes Vibration

A loose or worn idler bracket and spring can make your Spartan mower shake. The hole in the bracket where the spring attaches can wear larger and the spring can become stretched. When this happens, your will experience a vibration.

Replace a worn idler bracket or spring. Check the bearing and bushing in the engagement linkage and replace them if you find they are worn.

Debris Lodged in a Spartan Mower Causes Vibration

Check your Spartan mower for small debris stuck in the small crevices of the mower. When mowing the lawn, your mower kicks up debris that can collect on your mower. Something as small as a wood chip can cause extreme vibration in your mower.

Remove your spindle covers and clean off your deck regularly. Debris can collect under your pulleys and cause them not to sit flat and parallel to the deck.

Debris buildup can also affect the tensioner where it is no longer able to keep proper tension on the belt. This will cause extra slack and your mower deck to shake.

Look every part of your mower over carefully and remove any items that are lodged in your mower. It is best to clean your Spartan after each mowing to keep it free of debris not only to prevent vibration problems, but also corrosion from moisture in the debris.

Need help with cleaning procedures? Check out “How to Clean Your Mower for Best Performance“.