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How to Service a Riding Lawn Mower: Step-By-Step

Keeping your lawn mower in good working order by performing preventative maintenance checks and servicing your riding mower will minimize future problems. No one wants to be stuck in the middle of the yard for a problem that could have been avoided by regularly servicing your lawn mower.

Service a riding lawn mower by checking the safety system, changing fluids and filters; replacing spark plugs; checking the tire pressures; removing dirt and debris from the engine and hydraulic system areas; sharpening blades; scraping the deck; and checking for loose or damaged components.

Keep reading and I’ll share the steps to service your riding mower.

How to service a riding lawn mower

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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, knowledge or are not in the condition to perform the repair safely.

Checklist to Service a Riding Lawn Mower

A riding lawn mower should be serviced every 100 hours or annually, whichever comes first.

  • Check the safety systems
  • Check the battery
  • Change engine oil and filter
  • Replace spark plug
  • Replace fuel filter and inspect fuel lines
  • Check tire pressures & lug nuts
  • Clean or replace air filter if necessary
  • Remove dirt and debris from exhaust and engine areas
  • Remove debris around transmissions
  • Sharpen or change mower blades
  • Scrape the deck
  • Check condition of belts and pulleys
  • Lubricate the riding mower and mower deck
  • Clean and wash riding mower

Steps to Service a Riding Lawn Mower

Safety Precautions: When working on your riding mower, remove the spark plug wires and key to keep your mower from starting while servicing your mower and working on the mower deck. Always use jack stands or other comparable item that locks in place to raise your mower to gain access to the underside of the mower.

Collect Tools & Supplies

It is best to get all of the materials together before you start servicing your riding mower.

  • Engine Oil and Filter
  • Air Filter
  • Fuel Filter
  • Spark Plugs
  • Socket or Spanner Wrenches
  • Drain Pan, Funnel, Filter Wrench
  • Rags, Work Gloves, Safety Glasses, Work Surface Cover
  • Deck Scraper, Wire Brush or Metal Putty Knife

Check the Riding Mower Safety Systems

The riding mower includes a safety system that is there to keep you safe when you are running your riding mower. The engine should not start if your parking brake is not engaged. The engine should also cut out if you attempt to get out of your seat with the PTO engaged.

All of the safety devices installed on your lawn mower are necessary. Refer to your operator’s manual to find out how all safety devices work with your lawn mower and make sure they are working as designed.

Check the Battery on a Riding Mower

Most riding mower batteries are 12-volt batteries. Check your battery voltage using a voltmeter. If your battery reading is 12.6 volts or greater your battery is 100% charged. When the voltage reading is less than this, you need to charge your battery.

Make sure all cables are tight. Clean or replace the terminals if they are corroded.

Charge Your Riding Lawn Mower Battery

  • Disconnect the battery cables from the battery. Remember: Positive cable (Red +) is the last one off and first one on. Now, if the battery has removable caps check the water level. If the plates inside the battery are not covered with water you will need to add distilled water to them. Note: well water is not good for a battery. City water is a little better option, but it is best to use distilled water to your battery.
  • After checking the water level, hook the charger to the battery.
  • Check the battery voltage with your meter and see what it has in it. If the battery has 11.8 volts in it you won’t have to charge it very long. If it has 10.1 volts your battery is going to need to sit on a charger for a while. The lower the voltage reading, the longer your battery will need to sit on the charger.

    I like to put a very low battery on what is called a “slow bake”. Some battery chargers have different switches on them such as 6 amps, 4 amps or 2 amps. Charge a very low battery on 2 or 4 amps and let it charge for about an hour. After an hour, check the reading to make sure the voltage rate is increasing. If it is, continue to charge for another hour.

If you are preparing your battery for winter storage, read more about winter battery care here.

Change Engine Oil and Filter on your Riding Lawn Mower

Your engine oil and filter should be changed every 100 hours or annually to keep your engine lubricated with clean oil. Not changing your engine oil regularly can have damaging effects to the engine. Note: If your engine is new, you need to change the oil after the initial 5 hours.

Prepare Work Surface: Lay covering over your work surface to prevent spilled oil from penetrating the ground. Cardboard and newspaper work well.

Warm Engine Oil: Start your riding mower, park it on top of work surface cover, and let run for 2 to 3 minutes to warm the engine oil. Warm oil flows better than cool oil. Take caution when working around the hot engine.

Remove the Key & Unplug the Spark Plug Boot: Remove the ignition key and spark plug boot(s) to keep your mower from starting while servicing your riding mower. This is a necessary safety precaution to prevent serious injury.

Remove Engine Oil Plug: Open the hood and locate the oil drain plug on the lower side of the engine. Clean dirt and debris from the area around the oil plug so you don’t contaminate the engine when removing the oil plug. Place a drain pan under the oil plug, remove the plug and allow the oil to drain into the pan. Remove the oil fill cap to allow the oil to flow better.

Some riding mowers use an oil drain port where a hose is attached to drain oil. Open the drain port, attach the drain hose to the port and place the opposite end in the drain pan. Remove the oil fill cap to allow the oil to flow better.

Replace Engine Oil Filter & Oil Plug: Using a filter wrench, remove the oil filter and replace with a new filter. Once all of the oil has drained, reinstall the drain plug.

Fill with Engine Oil: Fill the crankcase with the quantity and type of engine oil recommended by your manufacturer. You must make sure you have a sufficient engine oil level. It cannot be too low or too high as either level can cause damage.

Start Engine and Check Oil Level: Reinstall the spark plug boots and start your engine for a few minutes. Turn the engine off and let the oil cool. Recheck the oil fluid level. Add more oil if needed.

Replace Spark Plug(s) on Your Riding Mower

Replace your spark plug(s) annually to make sure sure you have a good working spark plug. If you choose not to replace it, inspect your spark plug for excessive buildup on the plug. You will also be looking for any damage or a cracked porcelain insulator.

Replace Fuel Filter & Inspect Your Riding Mower’s Fuel Lines

Much of todays fuel includes ethanol. Ethanol is corrosive and not only develops a gummy product that may clog your fuel filter and fuel lines, it can also break down the plastic and rubber used in your filter and lines.

Replace the fuel filter and check your fuel lines for dry and brittle fuel lines. Replace old fuel lines. I recommend using worm gear clamps in place of pinch style clamps to prevent damages from the clamps.

Check Tire Pressures & Lug Nuts on Your Riding Mower

Check your lug nuts to ensure they are securely in place. Your tire pressures need to be at the level shown on the tire sidewalls. The tires need to have the same amount of pressure. Uneven pressures can cause you to have an uneven cut due to causing the mower deck to not sit level.

Clean or Replace Air Filter if Necessary on Your Riding Mower

Your riding mower’s engine needs clean air to operate efficiently. Without access to clean air, your engine is starved of air and will overheat. Inspect your air filter frequently, clean or replace with a new filter when necessary.

Remove the Air Filter from the Filter Housing: Remove your air filter being careful not to knock any dirt into the air intake. Wipe any dirt left in the housing with a dry clean cloth.

Remove Dirt from the Air Filter: Tap the air filter against a solid surface to knock loose dirt from the filter. Do not use an air compressor to blow your air filter clean.

Check Air Filter Condition: Hold the filter up to the light. You are looking for light through the paper element. If you can see light, the filter can continue to be used.  If you see any blockages of light, you need to replace with a new filter.

Remove Dirt and Debris from Exhaust, Engine & Transmission Areas in Your Riding Mower

Remove the engine shroud and remove all dirt and debris from around the engine and exhaust areas. Clean any dirt that built up on and around the engine cooling fins and heat shields. Buildup around the engine prevents air movement to keep the engine cool and prevent overheating. Continue to remove dirt around the riding mower’s transmission.

Check Condition of Your Riding Mower Belts, Pulleys & Spindle Housings

Worn belts and pulleys can cause your hydraulic pump or mower blades not to work properly. If your belts appear worn, cracked of have a glazed look to them, you need to replace them.

Over time, bearings can wear and become damaged in your pulleys. To check the bearings in your pulleys, grab a hold of each pulley and slowly turn the pulley to make sure it still moves smoothly. If you feel any resistance or sound from your bearing you need to replace the pulley.

Check for bearing wear in your spindle housing. Do this by grabbing a hold of each side of the mower blade while wearing a good pair of work gloves to protect your hands from sharp edges. Rock the blade in an up and down motion. If you feel movement, you need to replace the bearing or spindle housing assembly.

Note: Some manufacturers only allow you to rebuild a spindle housing, some only sell the spindle housing assembly while others offer both. Here are instructions to replace the bad bearing.

Repair Riding Mower Spindle Housing with a Bad Bearing 

Remove the Belt Off of the Pulley: Find something narrow to put between the belt and the groove of the bad pulley and carefully turn the belt by hand. Let the narrow object follow the belt to the pulley and pry up on the belt so it comes off of the pulley. 

Remove the Pulley: Get a socket that will fit the nut on top of the pulley and remove it. In most cases, it will be a normal thread so turn it to the left or counter clockwise. Depending on what type of mower you have, there may or may not be set screws holding the pulley onto the shaft. These may be allen screws or hex screws. They may not come off very easy and you may need to use a puller to remove. 

Remove the Spindle: There should be 4 to 8 bolts holding the spindle in place. Remove the bolts and the assembly will fall out of the bottom of the deck. 

Replace Bearing: Please the housing assembly on a flat hard work surface. Check to see what you will need to disassemble the housing. Sometimes a snap ring will hold it together and other times you will just replace the entire housing which includes the bearings. Replace the bearing if your assembly allows you to. Grease the bearing and attach it to the deck in the reverse steps you used to take it apart. 

Reinstall Housing, Pulley, and Belt: Once you bolted the housing to the deck and install the pulley, make sure everything is tight and there isn’t any movement. Reinstall the belt. Turn the belt by hand to make sure it is on all of the pulleys. 

Sharpen or Change Your Riding Mower Blades

Blades become worn after time from dirt and other debris in your yard. The dull blades can put strain on your riding mower and leave you with a poor cut. Inspect your mower blades for wear and damage. If you find a blade is bent or damaged, you need to replace your mower blades.

When reinstalling your mower blades after sharpening, make sure your blades are balanced. An unbalanced blade can cause vibration in your mower deck and an uneven cut. Read more about inspecting your mower blades and the different ways to sharpen your blade with my article “Inspect, Sharpen, and Replace Lawn Mower Blades”.

Scrape the Riding Mower Deck

Keeping the mower deck clean will provide you with a better cut and better mower performance. Buildup underneath the deck compromises the air movement needed to create a good cut. The mower blade is designed to create air movement in the deck.

The blade along with the suction created in the mower deck makes the grass blade stand tall so the blade can pass by and precisely cut the grass blade. Scrape the deck using a deck scraper or metal putty knife. A good stiff wire brush also works well.

Your mower may be equipped with a deck wash port. Follow your manufacturer’s instructions to attach the garden hose and use the port. You may still need to scrape your mower deck if it has significant buildup.

Lubricate the Riding Lawn Mower and Deck

Using a high performance multi-purpose grease, lubricate the idler arm pivots and grease zerks on your riding mower. Lubricate your pedal pivot points, deck spindles if they are serviceable, and front wheels. Refer to your operator’s manual to verify all grease and lubrication points on your mower.

Finish checking over your riding mower and secure all hardware. Finish removing all dirt on the and wash your mower. Allow the mower to completely dry before storing. Place your mower in the sun to dry or use a handheld blower.

Clean and Wash Your Riding Lawn Mower

Remove all other debris and wash your mower. Make sure it is completely dry by placing the mower in the sun to dry or using a handheld blower to speed up the drying process. Placing your mower in the sun will help all moisture to evaporate which is very beneficial to your electrical components.

Related Items

Winterize Your Riding Lawn Mower

There are additional steps to be taken at the end of the mowing season to prepare your mower for storage. You must stabilize the fuel in your lawn mower and take proper steps to secure your battery. Find out more information on winterizing a riding mower here.