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John Deere D125 Troubleshooting
The
John Deere D125 lawn tractor was manufactured from 2014 to 2017. The JD D125
powerline components: Briggs and Stratton 40R877 4-cycle V-twin cylinder OHV
air-cooled gasoline engine and Tuff Torq T40 belt-driven hydrostatic
transmission with infinite forward and reverse gears.
A 40.1 cubic inches (655 cc) engine has a cylinder bore of 2.97" (75
mm), piston stroke of 2.89" (73 mm), and rated power of 20 hp (14.9 kW).
Max. forward speed - 5.5 mph (8.8 km/h), maximum reverse speed - 3.2 mph
(5.1 km/h).
The John Deere D125 is equipped with a manual steering system, disc
brakes, 15x6.00-6 front tires, and 20x8.00-8 rear tires. The wheel base
is 49" (1240 mm). The lawn tractor is compatible with the following
attachments: 42" mid-mount 2-blade mower deck with cutting height of
1-4" (25-102 mm), 43.25" front-mount 2-stage snowblower with clearing
height of 18" (450 mm), and 46" front blade with mechanical lift system.
Engine Troubleshooting |
Engine will not start or starts up hard |
No gasoline in tank - Fill fuel up |
Wrong grade of gasoline - Use quality gasoline |
Water or air in fuel system - Remove air or water from system |
Defective spark plug wire connection - Inspect the spark plug wire connection, replace or repair |
Spark plug is defective - Change spark plug |
Fuel filter is plugged - Change fuel filter |
Brake pedal not pushed down - Push the brake pedal down |
Carburetor components worn out - Repair or replace parts |
Low cylinder compression - Check cylinder block and replace worn parts |
Improperly adjusted or worn throttle cable - Adjust properly or change the cable |
Clogged cooling fins - Need to wash or clean |
Ignition system failure - Check ignition system and replace faulty parts |
Stuck or faulty choke cable - Clean or replace the cable |
Air filter element is plugged - Replace or clean air filter |
Dirty or defective fuel pump - Clean or install new fuel pump |
Engine starts and stalls immediately |
Faulty spark plug - Replace spark plug |
Clogged or defective carburetor - Service or change carburetor |
Ignition coil is not working - Change ignition coil as required |
Loose or broken valve springs - Install new valve springs |
Valves are stuck - Valves must be cleaned |
Not enough engine oil - Fill the crankcase with engine oil |
Engine is overloaded - Load reducing is recommended |
Cooling fins are plugged - Clean and wash as required |
Carburetor mixture is too lean - Use proper settings |
Ignition timing is wrong - Set the ignition timing correctly |
Valve setting is improper - Set the valves correctly |
Engine knocking sound or abnormal noise |
Stale or low octane fuel - Use proper gasoline |
Engine overloaded - Reduce engine load |
Engine oil level low - Add oil to the engine crankcase |
Low idle speed set incorrectly - Test and adjust |
Fuel pump is faulty or clogged - Clean or install new fuel pump |
Main bearings or crankshaft wear - Change or repair worn components |
Excessive valve clearance - Need to adjust valve clearance |
Piston rings or cylinder bore are damaged - Replace defective components |
Carburetor is incorrectly adjusted or clogged - Clean or correctly adjust carburetor |
Dirty air filter element - Change or service air filter |
Clogged or defective fuel pump - Test fuel pump and change if necessary |
Ignition failure - Check ignition and replace faulty components |
Cylinder head gasket is blown - Replace cylinder head gasket |
Valves are burned or stuck - Change or service valves |
Push rod is worn or defective - Replace push rod |
Cylinder block parts are damaged - Defective parts need to be replaced |
Engine using too much gasoline |
Insufficient choke opening - Inspect choke cable and adjust as required |
Improper carburetor main jet adjustment - Adjust it properly |
Spark plug is loose or defective - Spark plug need to be tightened or replaced |
Valves are stuck, worn, or burned - Replace or clean valves |
Sleeve, piston, or rings are damaged - Replace defective components |
Valve clearance is not correct - Need to adjust valve clearance |
Excessive oil consumption |
Defective seals or gaskets - Install new components |
Damaged valve stems or valve guides - Change the valves |
Piston rings are seized or worn - Piston rings replacement required |
Scuffed piston or cylinder liner - Inspect piston and liner, replace as required |
Breather hose or pipe is blocked - Service or replace |
Hydrostatic Transmission Troubleshooting |
HST transmission noise |
Speed control linkage is worn or unadjusted - Adjust or replace linkage |
Transmission overload - Reduce loading |
Transmission fluid is dirty or fluid level is too low - Pour fresh fluid or add transmission fluid to proper level |
Worn or defective transmission components - After disassembly and inspection, replace defective components |
Shift linkage is rusty or worn - Lubricate or replace the linkage |
Hydrostatic pump is blocked or defective - Change or repair pump |
Unadjusted or damaged transmission shift control parts - Adjust correctly or replace |
Transmission fluid insufficient - Need to add transmission fluid |
Drive pulley is worn or faulty - Replace pulley |
Shifter linkage is faulty or not adjusted - Adjust properly or replace linkage |
Worn or out of adjustment speed control linkage - Adjust or repair linkage |
Damaged transmission seals or gaskets - Seals and gaskets need to be replaced |
Final drive shaft leaks - Replace shaft seals |
Cracked transmission housing - Install a new transmission housing |
Mower Deck Troubleshooting |
Mower vibrates too much |
Mower deck drive pulley is worn or dirty - Clean or change pulley |
Loose or damaged drive belt - Adjust belt tension or replace belt |
Warped or not balanced mower blades - Balance or change as needed |
Blade mounting bolts are loose - Bolts need to be tightened |
Constant clogging of discharge chute |
Ground speed is too fast - Operate at slower speed |
Tall grass - Adjust mower to lower cutting height |
Reduced engine speeds - Open choke fully |
Mower cuts too low - Change cutting height adjustment |
Drive belt installation is not correct - Install drive belt correctly |
Lawn mower leaving uncut grass |
Discharge area is clogged - Need to clean the mower deck |
Not sharp blades - Need a blade sharpening |
Worn or damaged blades - Replace the blades |
High mowing speed - Operate at slower speed |
Cutting level is too low - Must be set to high cutting height |
Bagger is full - Clean bagger |
Blades are scalping the grass |
Lawn is not level or bumpy - Lawn leveling required |
Low cutting height - Raise the cutting height |
Ground speed is too fast - Use a slower speed |
Improperly leveled mower deck - Level the deck correctly |
Blades are worn or bent - Replace the blades |
Tires are not properly inflated - Correct tire pressure |
Tire pressure is too low - Inflate tires as required |
Improperly leveled mower deck - Adjust the level of mower deck correctly |
Blades are excessively dull - Need a blade sharpening |
Blades are defective or worn - Blades must be changed |
Cutting deck is clogged - Clean mower deck as required |
Damaged mower deck shell - Repair or change the deck |
Loose or faulty mower spindle - Change or repair the spindle |
Electrical Troubleshooting |
Battery does not charge |
Loose or corroded electrical wiring connections - Tighten or clean electrical wiring connections |
Electrical terminal connectors are faulty - Terminal connectors should be replaced |
Battery failing - Replace the battery |
Low battery power - Battery is drained, recharge it |
Battery won’t hold charge - Service battery or change it |
Disconnected wiring or bad battery terminals - Connect wiring properly or install new terminals |
Battery is low or faulty - Recharge or replace battery |
Wiring is incorrectly connected or disconnected - Inspect wiring and connect correctly |
Battery capacity is low - Battery is drained, recharge it |
Incorrectly gapped or worn spark plug - Clean, gap or replace spark plug |
Starter motor or solenoid is defective - Starter/solenoid needs to be replaced |
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Lawn and Garden Tractors Technical Specs |