6 Most Common John Deere L120 Problems and Effective Fixes

The John Deere L120 features a powerful engine, smooth transmission, and easy-to-use controls, which make it a popular choice for homeowners with large lawns.

It has a cutting width of 48 inches, which allows for efficient mowing of larger areas. Despite these features, the L120 is prone to a few issues. The most common John Deere L120 problems are starting issues, transaxle problems, Worn-out hydro pump, excess smoke production, transmission problems, and abrupt stops.

We’ve taken the time to explore these issues and find simple, quick fixes. Read on.

Problematic Starts

Hard starting is the most prevalent John Deere l120 problem. Your John Deere l120 won’t crank due to a faulty battery, dirty oil, little oil, and a defective spark plug and recoil.

Old fuel is the primary cause of clogging. Fuel breaks down after some time, leaving behind a solid residue responsible for blocking. This mainly affects the fuel filter and lines.

Blocked fuel filters and lines prevent sufficient air flow, making starting your tractor difficult. It’s advisable to regularly clean fuel residues in the filters and lines to avoid clogging.

Your tractor’s battery is its primary energy source. As such, any battery defects will lead to a problematic start. The battery’s voltage shouldn’t read below 12.7 volts. Always recharge before reaching this voltage to avoid inconveniences.

Overused spark plugs and broken recoils cause starting difficulties. You should replace spark plugs after every one hundred hours for improved efficiency. Check the recoil for damaged parts and fix them immediately if possible.

Transaxle Problems

Transaxle leaking is a prevalent complaint among John Deere l120 owners. This issue causes severe damage to the tractor’s hydro pump and general functionality. Low oil levels are the primary causes of transaxle issues, and a surging feeling is the first sign of this problem.

To fix transaxle issues, remove the transaxle from the tractor, then drain and clean it. Afterward, refill the tank with new oil and ensure it reaches about one inch from the vent’s plug hole. You shouldn’t worry about overfilling the tank, as leaking from the top is harmless to the tractor.

Low-viscosity oils are the most preferable for John Deere tractors due to their cooled air engines. A good example is Hy-Gard oil.

The john deere l120 transaxle is impossible to service. According to the manufacturer, you should replace it in case of internal damage.

Worn-out Hydro Pump

If your tractor crawls after starting, high chances are that its hydro pump is spoilt. This is because John Deere hydro pumps wear out fast.

A faulty hydro pump can’t pump hot oil sufficiently, leading to a constricted tractor movement. The most predominant sign of this issue is a noisy pump, indicating strain.

To prevent this inconvenience, constantly monitor the tractor’s hoses, oil levels, and connectors for early detection.

Smoke Production

Smoke production is one of the most prevalent John Deere l120 problems. Although this issue may be alarming, especially to new owners, fixing it is easy and won’t cost you an engine replacement if dealt with immediately.

The L120 lawn tractor produces smoke when the ratio of oil to air in their systems is high. Smoke production happens due to clogged air filters, excess crankcase oil, little engine oil, and internal engine problems.

Clogged air filters, a result of debris and dirt build-up, curb sufficient airflow in the tractor. Excess oil in the crankcase exerts superfluous pressure on the engine and eventually flows into the cylinder, while low oil levels cause the engine to strain, producing excess heat.

Cleaning clogged air filters and draining excess oil should fix your tractor. You should also refill the tractor if the problem results from little oil. However, it’s advisable to take the machine to a mechanic in case of engine problems.

Abrupt Stops

John Deere l120 tractors are prone to stopping after running for hours. This issue results from working on wet grounds, which causes the tractor’s engine to strain. Lifting the tractor’s deck improperly when cutting dense grass may also lead to this issue.

Another reason for your tractor to stop working is a faulty spark plug. Change this gadget religiously, after every 100 hours, to avoid problems.

A damaged tractor blade will cause the tractor to shut down. Faulty blades lead to excessive vibrations, which trigger stalling.

A dull blade means the engine has to work harder, leading to an unexpected shut-off. Always ensure that the mower’s blade is in tip-top condition before starting work.

In case of prolonged and frequent shut-offs despite applying the tips above, take the machine to a mechanic, as the problem could be internal and significant.

John Deere L120 Transmission Problems 

Transmission issues are among the most prevalent John Deere L120 problems. You are likely to experience JD l120 transmission problems at some point. Primary causes of this issue include old hydraulic oil, low oil levels, and a faulty drive belt and tensioner pulley.

A faulty drive belt causes pump problems, which can be critical. Replace it immediately in case of wearing out, fraying, or cracking.

To fix a faulty tensioner pulley, grease the arm and replace the pulley. Old and low oil levels don’t lubricate the hydraulic system sufficiently, leading to transmission difficulties. Change the hydraulic oil and monitor its levels regularly to prevent this issue.

John Deere L120 Review

After examining John Deere l120 issues, it’s now time to look at a complete review of this lawn tractor. Despite its small size, the John Deere l120 is packed with impressive attributes. It features infinite gears you can control from the foot pedals, promoting smooth operation.

Built with 18 inches turning radius and 4×2 2WD chassis, the John Deere l120 is ideal for lawns with small grass patches requiring cutting. Its top speed of 8.8km/h makes it perfect for small and large gardens. The JD l120 operates on the Briggs and Stratton 40  or CV 40 gasoline engines, making it highly reliable.


The JD l120 lawn tractor is susceptible to several problems. The leading John Deere l120 problems are smoke production, transaxle leaking, problematic starts, and running issues. Fix your tractor using the tips in this article to avoid passing out on its benefits.