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John Deere LA125 Troubleshooting

The John Deere LA125 is a LA105 series lawn tractor. This model was manufactured between 2008 to 2010. The John Deere LA125 driveline includes a 32.9 cu.in (540 cc) Briggs and Stratton 331877 4-cycle vertical-shaft single cylinder air-cooled gasoline engine and Tuff Torq T40 Belt-driven hydrostatic transmission with infinite forward and reverse gears.

The engine has a cylinder bore of 3.7" (94 mm), piston stroke of 3.06" (78 mm), and rated power of 21 hp (15.3 kW). Max. forward speed - 5.5 mph (8.8 kph), maximum reverse speed - 3.2 mph (5.1 kph).

The John Deere LA125 is equipped with a manual steering system, disc brakes, 15x6.00-6 front tires, and 20x8.00-8 rear tires. The wheelbase is 49" (1240 mm). Compatible attachments for the tractor: a 42" mid-mount 2-blade mower deck with manual lift and cutting height of 1.0-4.0 in (25-102 mm), 46" front-mount blade with lifting height of 6" (150 mm), and 44" front-mount 2-stage snow blower with clearing height of 18" (450 mm).

Engine Troubleshooting
Engine starts up hard or doesn't start
Gas tank is empty - Fill fuel up
Low-quality gasoline - Use quality gasoline
Air or water in fuel system - Remove water or air from fuel system
Spark plug wire connection are damaged - Check spark plug wiring connection, repair or change
Spark plug is faulty - Change spark plug as required
Plugged fuel filter - Change fuel filter
Brake pedal not pushed down - Push the brake pedal down
Problems with carburetor adjustment - Adjust as required
Low engine compression - Inspect cylinder block and change defective components
Throttle cable is adjusted improperly or worn - Replace cable or adjust properly
Engine runs unevenly
Clogged cooling fins - Need to wash or clean
Defective ignition system - Check ignition and replace faulty components
Throttle cable is stuck or faulty - Replace or service the cable
Air filter is dirty - Service or change air filter
Clogged or defective fuel pump - Clean or replace fuel pump
Engine starts and then stalls
Faulty spark plug - Spark plug need to be replaced
Carburetor is clogged or faulty - Clean or install new carburetor
Defective ignition coil - Ignition coil must be replaced
Broken or bad valve springs - Install new valve springs
Valves sticking - Valves must be cleaned
Engine overheating
Insufficient engine oil - Add oil to the engine crankcase
Excessive engine load - Load reducing required
Air intake grill is clogged - Wash or clean as required
Too lean carburetor mixture - Set the carburetor correctly
Ignition timing is improper - Set the ignition timing properly
Wrong valve setting - Valves needs to be set correctly
Engine knocking sound or abnormal noise
Low octane fuel - Use correct fuel
Engine is overloaded - Load reducing required
Engine oil level is low - Fill up the engine oil
Wrong adjustment of low idle speed - Adjust idling as required
Dirty or faulty fuel pump - Service or replace fuel pump
Crankshaft or main bearings are worn out - Repair or replace defective parts
Valve clearance is wrong - Need to adjust valve clearance
Worn piston rings or cylinder bore - Replace defective parts
Engine loses power
Clogged or incorrectly adjusted carburetor - Adjust the carburetor properly or clean it
Dirty air filter element - Change or service air filter
Fuel pump is clogged or faulty - Test fuel pump and replace if necessary
Ignition system is defective - Inspect ignition system and change faulty parts
Blown cylinder head gasket - Install new head gasket
Burned or stuck valves - Replace or service valves
Push rod is bent or worn - Push rod should be replaced
Faulty cylinder block parts - Replace defective parts as required
Engine using too much gasoline
Choke opening is not full - Replace or adjust choke cable
Improper carburetor main jet adjustment - Adjust main jet as required
Spark plug is loose or defective - Tighten or change the spark plug
Valves are worn, stuck, or burned - Change or service valves
Worn rings, piston, or sleeve - Change faulty components
Valve clearance is incorrect - Adjustment procedure required
Excessive engine oil consumption
Damaged gaskets or seals - Install new components
Valve guides and stems are worn - Valves need to be changed
Piston rings are stuck or worn - Replace piston rings
Scored cylinder liner or piston - Check liner and piston, change as required
Clogged breather pipe or hose - Clean or change

Hydrostatic Transmission Troubleshooting
Hydrostatic transmission makes excessive noise
Speed control pedal linkage is bent or not adjusted - Change or adjust linkage
Excessive transmission load - Reduce loading
Fluid is contaminated or fluid level is insufficient - Top up to proper level or change transmission fluid
Transmission parts are worm or defective - Check transmission parts for defects and change if necessary
Difficult to shift
Shift linkage is worn or rusty - Replace or lubricate the linkage
Hydrostatic pump is defective or blocked - Change or repair pump
Worn or misadjusted transmission shift control parts - Adjust correctly or replace
Power is insufficient
Transmission oil level is low - Check and refill the transmission oil
Faulty or worn drive sheave - Install a new sheave
Shifting linkage is misadjusted or broken - Adjust properly or replace linkage
Worn or out of adjustment speed control linkage - Replace or adjust linkage
Transmission leaks
Transmission seals or gaskets are broken - Replace seals or gaskets
Final drive shaft is leaking - Change shaft seals
Cracked transmission case - Change broken case

Mower Deck Troubleshooting
Mower vibrates too much
Damaged or clogged mower drive pulley - Replace or clean pulley
Drive belt is defective or loose - Belt needs to be adjusted or replaced
Unbalanced or warped cutting blades - Replace or balance blades
Blade mounting bolts are loose - Bolts should be tightened
Constant clogging of discharge chute
High ground speed - Use a slower speed
Grass is too long - Adjust mower to lower cutting height
Reduced engine rpm - Open throttle fully
Cutting level is too low - Use a higher cutting height
Mower drive belt installation is improper - Reinstall drive belt properly
Lawn mower leaving uncut grass
Cutting deck clogging - Check cutting deck and clean as necessary
Blades are excessively dull - Need a blade sharpening
Worn or damaged blades - Install new blades
Fast mowing speed - Select a lower speed
Mower cuts too low - Must be set to high cutting height
Bagger is full - Remove grass from bagger
Blades are scalping the grass
Bumpy or unleveled lawn - Roll or level the lawn
Cutting level is too low - Raise the cutting height
High mowing speed - Select a lower speed
Deck is not leveled correctly - Level the deck properly
Worn or bent blades - Blades need to be replaced
Low tire inflation - Check and inflate the tires
Uneven cut
Low tire inflation - Inflate tires correctly
Improperly leveled mower deck - Level the deck correctly
Excessive blade dullness - Need a blade sharpening
Blades are defective or worn - Change the blades
Deck clogged with grass clippings - Clean out the mower deck
Damaged mower deck shell - Repair or change the deck
Mower spindle is loose or defective - Replace or repair the spindle

Electrical Troubleshooting
Battery cannot be charged
Corroded or loose cable connections - Clean or tighten wiring connections
Battery terminal connectors are faulty - Terminal connectors need to be changed
Worn-out battery - Change the battery
Starter cranks slowly
Low battery voltage - Battery needs to be recharged
Battery is not holding charge - Service charging system or replace battery
Disconnected cables or faulty battery terminals - Check battery wires and service or replace terminals
Starter motor is not working
Battery is drained or defective - Recharge or change battery
Battery wires are disconnected or incorrectly connected - Check wires and connect correctly
Low battery capacity - Charge the battery
Spark plug faulty or incorrectly gapped - Replace or clean and gap
Starter motor or solenoid is defective - Replace solenoid or repair starter




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