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John Deere LA120 Troubleshooting
The
John Deere LA120 lawn tractor was manufactured from 2007 to 2009. The John Deere
LA120 driveline consists of Briggs and Stratton 441677 4-cycle V-twin cylinder
OHV vertical-shaft air-cooled gasoline engine and Tuff Torq T40 belt-driven
hydrostatic transmission with infinite forward and reverse gears.
A 44.2 cu.in (724 cc) engine has a cylinder bore of 3.12" (79 mm),
piston stroke of 2.89" (73 mm), and rated power of 21 hp (15.7 kW). Max.
forward speed - 5.5 mph (8.8 kph), maximum reverse speed - 3.2 mph (5.1
kph).
The tractor was equipped with a manual steering system, disc brakes,
15x6.00-6 front tires, and 20x10.00-8 rear tires. The wheel base is 49
in (1240 mm). The John Deere LA120 is compatible with a 42" mid-mount
2-blade mower deck with cutting height of 1.0-4.0" (25-102 mm) and
mechanical lifting system.
| Engine Troubleshooting |
| Engine will not start or difficult to start |
| Fuel tank is empty - Fill it up |
| Wrong fuel grade - Use quality fuel |
| Air in fuel system - Bleed fuel system |
| Disconnected or loose spark plug wire - Inspect spark plug wiring connection, change or repair |
| Faulty spark plug - Replace spark plug |
| Fuel filter is dirty - Install new filter |
| Safety contact for brake pedal defective - Install new part |
| Carburetor is not adjusted - Check carburetor float adjustment |
| Bad engine compression - Inspect cylinder block and replace worn components |
| Throttle cable is adjusted incorrectly or damaged - Replace cable or adjust correctly |
| Air intake grill is clogged - Wash or clean as required |
| Ignition system failure - Check ignition and replace faulty components |
| Stuck or defective throttle cable - Replace or service the cable |
| Air filter element is plugged - Clean or replace air filter |
| Fuel pump is dirty or defective - Service or replace fuel pump |
| Engine starts but stalls immediately |
| Damaged spark plug - Change spark plug as required |
| Carburetor is faulty or dirty - Clean or change carburetor |
| Defective ignition coil - Replace ignition coil as necessary |
| Valve springs are bad or broken - New valve springs need to be installed |
| Valves are stuck - Clean the valves |
| Not enough engine oil - Fill up the engine oil |
| Engine overload - Reduce load |
| Air intake screen is blocked - Clean and wash as required |
| Too lean carburetor mixture - Use proper settings |
| Improper ignition timing - Adjust ignition timing as required |
| Improper valve setting - Adjust valves as required |
| Low octane fuel - Use proper gasoline |
| Engine is running overloaded - Reduce engine load |
| Not enough engine oil - Fill up the engine oil |
| Low idle speed setting is incorrect - Correct idle adjustment |
| Clogged or defective fuel pump - Service or replace fuel pump |
| Main bearings or crankshaft failure - Have bearings or crankshaft replaced |
| Incorrect valve clearance - Check and adjust |
| Damaged cylinder bore or piston rings - Replace faulty parts |
| Incorrectly adjusted or clogged carburetor - Clean or correctly adjust carburetor |
| Air filter element is clogged - Service or replace air filter |
| Fuel pump is defective or dirty - Check fuel pump and replace if necessary |
| Ignition failure - Check ignition and replace faulty components |
| Blown cylinder head gasket - Cylinder-head gasket replacement required |
| Stuck or burned valves - Service or replace valves |
| Bent or worn push rod - Push rod needs to be changed |
| Cylinder block components are faulty - Replace defective parts as required |
| Throttle did not open fully - Replace or adjust throttle cable |
| Improper carburetor main jet adjustment - Adjust it correctly |
| Loose or faulty spark plug - Replace or tighten spark plug |
| Valves are stuck, burned, or worn - Change or clean valves |
| Worn sleeve, rings, or piston - Replace defective components as required |
| Valve clearance is not correct - Adjustment procedure required |
| Engine consuming too much oil |
| Damaged gaskets or seals - Replace to repair leaks |
| Valve stems or guides are damaged - Install new valves |
| Seized or wear piston rings - Replace piston rings |
| Scored piston or cylinder liner - Check liner and piston, change as required |
| Breather pipe or hose is clogged - Replace or service |
| Hydrostatic Transmission Troubleshooting |
| HST transmission makes excessive noise |
| Speed control linkage is worn or unadjusted - Adjust or repair linkage |
| Excessive transmission load - The load should be reduced |
| Insufficient oil level or contaminated oil - Change transmission oil or top up to proper level |
| Transmission components are damaged or worn - Change or repair defective parts |
| Rusty or worn shift linkage - Install a new gear linkage |
| Hydrostatic pump is worn or stuck - Repair or replace pump |
| Faulty or misadjusted transmission shift control parts - Adjust properly or change |
| Transmission oil insufficient - Check and refill the transmission oil |
| Drive sheave is worn or faulty - Replace sheave |
| Shifting linkage is misadjusted or broken - Replace or adjust linkage |
| Speed control pedal linkage is damaged or out of adjustment - Adjust or change linkage |
| Transmission seals or gaskets are broken - Seals and gaskets need to be replaced |
| Final drive shaft leaks - Change shaft seals |
| Transmission housing is cracked - Install a new transmission housing |
| Mower Deck Troubleshooting |
| Mower vibrates excessively |
| Mower deck drive pulley is worn or dirty - Change or clean pulley |
| Drive belt is worn or loose - Change belt or adjust belt tension |
| Mower blades are not balanced or warped - Balance or change blades |
| Loose blade mounting bolts - Bolts need to be tightened |
| Discharge chute is constantly plugged |
| High mowing speed - Operate at slower speed |
| Grass is too long - Use a lower cutting height |
| Engine is running at too low speed - Throttle is not fully open |
| Low cutting height - Adjust mower to higher cutting height |
| Drive belt installed improperly - Check drive belt for correct installation |
| Mower deck is clogged - Mower deck needs to be cleaned |
| Not sharp blades - Sharpen the blades |
| Worn or defective blades - Blades must be changed |
| Mowing speed is too high - Use a lower speed |
| Low cutting height - Must be set to high cutting height |
| Grass bag is full - Clean grass bag |
| Blades are scalping the grass |
| Lawn is not level or bumpy - Level the lawn |
| Mower deck set to low cutting - Must be set to high cutting height |
| High ground speed - Need to slow down |
| Incorrect level of mower deck - Adjust mower deck level properly |
| Damaged or bent blades - Install new blades |
| Tires are not properly inflated - Inflate tires as required |
| Tires are not correctly inflated - Check and inflate the tires |
| Improperly leveled mower deck - Level the deck properly |
| Not sharp blades - Sharpen the blades |
| Blades are worn or damaged - Install new blades |
| Cutting deck clogging - Mower deck needs to be cleaned |
| Damaged mower deck shell - Replace or repair the deck |
| Loose or defective mower spindle - Repair or replace the spindle |
| Electrical Troubleshooting |
| Battery cannot be charged |
| Electrical wire connections are loose or corroded - Clean or tighten wiring connections |
| Electrical terminal connectors are defective - Replace terminal connectors |
| Dead cell in battery - Battery change required |
| Low battery capacity - Charge the battery |
| Battery won’t hold charge - Battery needs to be serviced or replaced |
| Battery terminals are corroded or wires are disconnected - Check cables and replace or service terminals |
| Starter motor is not working |
| Battery is low or faulty - Replace or charge as required |
| Battery wiring is disconnected or improperly connected - Inspect wiring and connect as required |
| Low battery capacity - Recharge the battery |
| Improperly gapped or dirty spark plug - Clean, gap or change spark plug |
| Starter motor or solenoid is defective - Change solenoid or repair starter |
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| Lawn and Garden Tractors Technical Specs |
