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John Deere S120 22 HP Lawn Tractor: A Step-by-Step How-To

Jordan

May 3, 2026

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Get Rolling: Mastering the John Deere S120 22 HP

We’ll walk through pre-start checks, fluids, deck setup, operation, maintenance, troubleshooting, and seasonal storage so we confidently operate and enjoy our John Deere S120 22 HP safely all year long.

Walk the perimeter and perform a visual sweep before we touch the key.

Check these key items on every walkaround:

Use the dipstick to check engine oil level and top with the manufacturer-recommended SAE grade if low. Tighten the fuel cap and smell around the tank for leaks.

Examine battery terminals for corrosion; loosen, clean with a baking soda/water paste if needed, and tighten connections snugly. Clear the work area of toys, rocks, sticks, and hidden wires to avoid accidents and damage.

Use fresh, clean gasoline and add stabilizer if we’ll store the tractor; drain old gas that smells sour or shows water in the bottom of the tank.
Change engine oil after the initial break‑in and then per the hour schedule; replace the oil filter with every oil change and recycle used oil responsibly.
Inspect and clean or replace the air filter—replace if it’s dark, oily, or crushed; a clogged filter makes the S120 run hot and sip more fuel.
Check coolant level on liquid‑cooled variants, otherwise clear the engine’s cooling fins of grass and debris to prevent overheating.
Top transmission/hydrostatic fluid to the recommended level if our model requires it and follow John Deere specs.

Use a simple test: if the engine hesitates under load, start with the air filter and fuel quality—those two are most often the culprit.

Sit comfortably, fasten our seatbelt if equipped, and keep the parking brake engaged while we prepare to start.

Place the throttle in the choke or start position when cold, set the PTO (power take-off) to off, and ensure the transmission is in neutral.

Turn the key and listen for any unusual noises. Listen for a steady, brisk crank; recognize that a brief crank is normal, but repeated hard cranking signals battery or starter issues—stop and diagnose if that happens.

Allow the engine to warm for a minute, then gradually move the throttle to a mid-range to test responsiveness. Familiarize ourselves with forward and reverse controls, the deck lift lever, cruise/ground-speed settings, and blade engagement—practice each control at low speed in an open area to build confidence (for example, engage blades briefly on a test strip of grass).

Safe stopping — do these steps in order:

Practice these steps regularly to build muscle memory and keep us safe on uneven ground.

Level the deck and set the cutting height for our grass: raise it in hot, shady periods and lower it for cool-season growth, but never scalp — for example, move the height up 1–2 notches in summer stress or down slightly in peak spring growth.

Inspect the blades for sharpness and balance; we sharpen or replace dull blades because torn grass invites disease. Sharpen on a bench grinder or take blades to a shop, then torque blade bolts to the spec in our manual.

Engage the PTO only when blades and area are clear of people, pets, and debris; verify nobody is nearby before switching blades on.

Overlap passes by about 25% for an even cut. Keep a steady ground speed to avoid scalping—if the tractor bogs, slow down or raise the deck. Vary mowing directions between jobs to prevent ruts and encourage upright growth. Mow slopes up and down rather than across for traction and safety.

Clean under the deck after mowing to remove clippings and buildup that reduce airflow and cut quality.

Inspect daily for debris and clogged cooling fins; remove grass, twigs, and buildup under the deck and around the engine to prevent overheating.
Check weekly fluid levels: engine oil, coolant (if equipped), and fuel; top off as needed.

Change oil and filters per the hour schedule (for example, every 50–100 hours depending on conditions) and replace the air filter sooner in dusty work.
Grease fittings and check belt tension; replace belts with cracks, glazing, or frayed edges.

Clean battery terminals and ensure the battery is securely mounted; test charge if starting becomes slow.
Keep a simple log of our hours and maintenance tasks so we know when to service components.

Troubleshoot quickly:

Contact a certified John Deere dealer when issues exceed our skills to ensure correct diagnosis and repairs.

Clean the tractor thoroughly, removing grass clippings and debris; park on a flat surface and block the wheels if we’ll leave it unattended for a few weeks.
Add fuel stabilizer to the tank and run the engine a few minutes to circulate treated fuel.
Change the oil and filter before long-term storage; disconnect the battery or use a smart maintainer to prevent drain.
Cover the tractor or store it indoors; if we expect heavy moisture or salt, store inside.

Fog the engine cylinders with a recommended fogging oil if the manual suggests it and lubricate pivot points, linkages, and grease zerks to prevent corrosion.

Consider upgrades like a mulching kit, rear bagger, LED light kit, or a cold-weather cab. Confirm compatibility, read installation instructions, and consult our dealer for wiring or large installs to keep the S120 performing and valuable.

You’re Ready

We’ve covered checks, fluids, controls, mowing, maintenance, storage, and upgrades—follow these steps and our routine to enjoy reliable S120 performance for years. Will we keep it running optimally together always?