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John Deere LA120 Tractor Problems

Gasoline Engine Problems

John Deere LA120 Engine fails to start

Fuel tank is empty - Fill it up.
Wrong grade of gasoline - Change fuel.
Stale gasoline - Drain fuel and replace with fresh fuel.
Fuel system clogged - Repair or replace.
Spark plug wire is loose or disconnected - Check the spark plug wires.
Spark plug damaged - Clean, adjust gap or replace.
Fuel filter is clogged - Replace fuel filter.
Safety contact for brake pedal defective - Install new part.
Carburetor is not adjusted - Check carburetor float adjustment.
Inspect starter cranking speed RPM. Compression problems.

Engine hard starting

Spark plug failed - Test spark and replace as required.
Problems with carburetor adjustment - Adjust as required.
Clogged fuel pipes - Servicing fuel system.
Choke cable damaged - Replacement required.
Stale or incorrect fuel - Drain and add proper fuel.
Electrical connection problems - Check and replace.
Starter is not working - Check the starter and replace defective components.

Rough running engine

Plugged cooling fins - Remove dirt from cooling fins.
Loose electrical contacts - Inspect and replace defective contacts.
Ignition adjust incorrect - Check spark plug and ignition.
Throttle cable sticks - Repair or replace.
Air filter dirty - Replace air cleaner.

Engine misses under load

Spark plug fail - Change spark plug.
Carburetor malfunction - Inspect and overhaul.
Ignition coil air gap incorrect - Check and adjust ignition coil air gap.

John Deere LA120 Engine overheats

Excessive engine load - Reduce loads.
Air intake screen blocked - Clean dirty components.
Engine oil high or too low - Check oil pump for wear or damage.
Improper engine oil viscosity - Change oil.
Check connecting rod to crankshaft bearing clearance.
Fast idle speed - Adjust fast idle.

Engine will not idle

Poor spark plug contact - Adjust spark plug gap.
Spark plug malfunction - Test spark and replace as required.

Engine knocking

Low octane gasoline - Use proper gasoline.
Engine overloaded - Reduce the load.
Lack of engine oil - Add engine oil.
Engine is running at low revs - Adjust carburetor.
Piston rings and cylinder bore worn - Replace damaged parts.
Check for engine overheating from plugged cooling fins.
Inspect and adjusting crankshaft end play.
Checking for wear crankshaft or camshaft bearings.

JD LA120 Engine backfires

Inspect spark plug and change if required.
Inspect and adjust choke.
Adjust carburetor idle mixture screw.
Inspect and adjust ignition coil air gap.
Inspect inlet and outlet valves.
Check valve clearance, adjust if required.
Check flywheel key.

Loss of power

Engine overheats - Clean or replace air filter.
Too much oil in engine - Excess oil needs to be drained.
Fuel pump is damage - Test fuel pump output.
Faulty governor - Checking and adjusting governor.
Inspect carburetor for plugged passages.
Checking engine compression.

Engine getting too much fuel

Insufficient throttle opening - Replace throttle cable.
Carburetor problems - Check carburetor float adjustment.

Black smoke is emitted during operation

Air filter is dirty or oil soaked - Clean or change filter.
Throttle not fully engaged - Inspect and adjust choke.
Check and adjust carburetor float level.

John Deere LA120 Electrical Troubleshooting

Starter doesn't work or will not turn engine

Blown fuse - Installing new fuse.
Poor terminal connection - Inspect and clean terminals.
Low charging voltage - Charge the battery.
Ignition switch defective - Replace switch.
Faulty starter - Repair or replace.
Wiring disconnected - Reconnect wires.

Battery doesn't charge

Battery cells defective - Replace the battery.
Bad contact between battery pole and cable - Check and Clean.

No Lights work

Light connector defective.
Bulbs defective.
Check wiring for short circuit.

JD LA120 Mechanical Troubleshooting

Excessive tractor vibration

Implements drive belts damaged or worn - Check and replace worn belt.
Worn traction drive belt - Check and replace belt.
Drive pulley malfunction - Clean the sheaves.
Unbalancing or bending of blades - Replace damaged blades.

Machine does not move while engine is running

Parking brake is applied - Unlock park brake.
Bypass lever is on - Deactivate the bypass valve.
Mower blades are loose - Fasten the blades securely.
Poor blade balancing - Check mower blade balancing.
Lack of oil in transmission - Add oil to the transmission.

John Deere LA120 Mower Deck Troubleshooting

Discharge Chute Clogged

Speed too high - Choose recommended speed.
Grass has grown too long - Use a shorter cutting height.
The grass is wet - Wait until the grass dries.
Low engine speeds - The throttle is not fully open.
Airflow restriction - Set higher revs.
Lack of cutting height - Use higher cutting.
Incorrect belt installation - Reinstall the belt properly.

Lawn mower leaving uncut grass

Clog in discharge area - Need to clean the mower deck.
Blade wornout - Sharpen the blade or install a new one.
Mower deck low - Checking and adjust deck height.
Grass bag overfilled - Clean grass bag.
Speed too high - Choose recommended speed.

Slipping drive belt

Pulley is dirty - Clean or replace.
Worn belt - Install new belt.
No belt tension required - Adjust belt tension.

Excessive mower vibration

Mower clogged or in pulleys - Remove clogging from mower deck or sheaves.
Damaged sheaves or belt - Replace damaged parts.
Belt or pulleys no adjustment - Check and adjust.
Blades out of balance - Balance blades correctly.

Blade strips grass

Cutting height improper - Set the proper cutting height.
Mower rollers not adjusted improperly - Adjust front or back wheel height.
Tire pressure is uneven - Inflate tires as required.
High blade speed during mowing - Blade speed required.
Bent blades during operation - Remove bent blade and install new one.

Uneven cutting results

Mower deck low - Level mower deck.
Low tire pressure - Inflate tires as required.
Wrong rollers position - Adjust mower deck wheels.
Ground speed too fast - Choose recommended speed.
Blades blunt - Installing new blade.

JOHN DEERE TRACTORS ATTACHMENTS
420	430	455	790	990
X300	X320	X330	X350	X475
X485	X500	X540	X570	X590
X700	X720	X738	X758	1023E
2025R	2210	2520	3025E	3032E
3038E	3038R	3039R	3046R	3203
3320	3520	4052R	4066R	4100
4105	4115	4200	4310	4320
4400	4410	4520	4600	4720

JD TRACTORS TROUBLESHOOTING
2640	3040	3310	3650	4100
5050D	5090R	5410	6105R	7200R
E130	L111	LA110	LT155	X300R