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John Deere STX30 Engine

John Deere STX30 Engine Specifications

Engine Model ............ Kohler Command CV12.5S
Engine Type ............ Gasoline, 4-cycle vertical shaft, 1-cylinder
Number of Cylinder ............ Single
Piston Displacement, cc (cu.in) ............ 398 (24.3)
Engine Bore, mm (in) ............ 87.0 (3.43)
Engine Stroke, mm (in) ............ 67.0 (2.64)
Engine Power, Hp (kW) ............ 12.5 (9.33)
Maximum Torque, Nm (ft-lb) ............ 27.8 (20.5)
Fast Idle Speed, rpm ............ 2500
Low Idle Speed, rpm ............ 1500
Compression Ratio ............ 8.5:1
Cooling System ............ Air Intake
Air Cleaner ............ Replaceable, high density paper element
Fuel System Type ............ Carburetor
Carburetor Type ............ Float Fixed Main Jet
Carburetor Model ............ Walbro or Nikki
Fuel Pump ............ Diaphragm Type Mechanical Pump
Fuel Filter ............ In-line
Governor ............ Centrifugal Mechanical Flyweight
Lubrication System Type ............ Full-Pressure
Ignition System Type ............ Dependable electronic magneto
Electrical System Rating, Volts ............ 12
Alternator Charging Capacity, Amp ............ 13

John Deere STX30 Engine Maintenance Data

Engine Oil and Filters

Engine Oil Type ............ SAE 5W-20/5W-30
Oil Classification ............ SG, SH, SJ or higher
Oil Capacity, L (qts) ............ 1.9 (2.0)
Oil Filter Part Number ............ AM125424
Air Filter Part Number ............ AM121608

Carburetor Adjustment

Main Fuel ............ Not adjusting
Idle Fuel ............ Adjust by needle and spring with limiter cap
Low Idle Speed, rpm ............ 1400±75
High Idle Speed, rpm ............ 3600±50

Valve Adjustment

Intake Valve Clearance ............ 0.04-0.08 mm (0.0015-0.0030 in.)
Exhaust Valve Clearance ............ 0.05-0.09 mm (0.0020-0.0035 in.)
Intake Valve Stem to Valve Guide Clearance ............ 0.038-0.076 mm (0.0015-0.0030 in.)
Exhaust Valve Stem to Valve Guide Clearance ............ 0.050-0.088 mm (0.0020-0.0035 in.)
Nominal Valve Seat Angle ............ 45 degrees

Ignition System

Spark Plug ............ Champion RC12YC
Spark Plug Thread Size, mm (in) ............ 14 (0.55)
Spark Plug Reach, mm (in) ............ 19.1 (0.75)
Spark Plug Gap, mm (in) ............ 1.02 (0.040)
Ignition Module Air Gap, mm (in) ............ 0.200-0.300 (0.0078-0.0118)
Spark Plug Torque, Nm ............ 24.4-29.8

John Deere STX30 Engine Service Data

Cylinder Block

Cylinder Bore I.D (Std) ............ 87.000-87.025 mm (3.4252-3.4262 in.)
Cylinder Bore I.D (Maximum Wear Limit) ............ 87.063 mm (3.4277 in.)
Cylinder Bore I.D (Max. Out of Round) ............ 0.12 mm (0.0047 in.)
Cylinder Bore I.D (Max. Taper) ............ 0.05 mm (0.0020 in.)
Crankshaft End Play (free) ............ 0.0575-0.4925 mm (0.0022-0.0193 in.)
Crankshaft End Play (thrust bearing with shims) ............ 0.050-0.530 mm (0.0020-0.0209 in.)
Crankshaft Bore in Crankcase I.D (Std) ............ 44.965-44.990 mm (1.7702-1.7712 in.)
Crankshaft Bore in Crankcase (Maximum Wear Limit) ............ 44.9758-45.0012 mm (1.7707-1.7717 in.)
Connecting Rod Journal O.D (Std) ............ 38.958-30.970 mm (1.5338-1.5343 in.)
Connecting Rod Journal O.D (Maximum Wear Limit) ............ 38.94 mm (1.5328 in.)
Connecting Rod Journal (Max. Taper) ............ 0.012 mm (0.0005 in.)
Connecting Rod Journal (Max. Out of Round) ............ 0.025 mm (0.0010 in.)

Cylinder Head and Valves

Cylinder Head (Max. Out of Flatness) ............ 0.076 mm (0.003 in.)
Hydraulic Valve Lifter to Crankcase Running Clearance ............ 0.0124-0.0501 mm (0.0005-0.0020 in.)
Intake Valve Stem-to-Valve Guide Running Clearance ............ 0.038-0.076 mm (0.0015-0.0030 in.)
Exhaust Valve Stem-to-Valve Guide Running Clearance ............ 0.050-0.088 mm (0.0020-0.0035 in.)
Intake Valve Guide I.D (Std) ............ 7.038-7.058 mm (0.2771-0.2779 in.)
Intake Valve Guide I.D (Maximum Wear Limit) ............ 7.134 mm (0.2809 in.)
Exhaust Valve Guide I.D (Std) ............ 7.038-7.058 mm (0.2771-0.2779 in.)
Exhaust Valve Guide I.D (Maximum Wear Limit) ............ 7.159 mm (0.2819 in.)
Valve Guide Reamer Size (Std) ............ 7.048 mm (0.2775 in.)
Valve Guide Reamer Size (0.25 mm Oversize) ............ 7.298 mm (0.2873 in.)
Intake Valve Minimum Lift ............ 8.96 mm (0.353 in.)
Exhaust Valve Minimum Lift ............ 9.14 mm (0.360 in.)
Nominal Valve Seat Angle ............ 45 deg

Piston and Piston Rings

Piston to Piston Pin (selective fit) ............ 0.006-0.017 mm (0.0002-0.0007 in.)
Piston Pin Bore I.D (Std) ............ 19.006-19.012 mm (0.7483-0.7485 in.)
Piston Pin Bore I.D (Maximum Wear Limit) ............ 19.025 mm (0.7490 in.)
Piston Pin O.D (Std) ............ 18.995-19.000 mm (0.7478-0.7480 in.)
Piston Pin O.D (Maximum Wear Limit) ............ 18.994 mm (0.74779 in.)
Top Compression Ring to Groove Side Clearance ............ 0.034-0.100 mm (0.0013-0.0039 in.)
Middle Compression Ring to Groove Side Clearance ............ 0.040-0.080 mm (0.0016-0.0032 in.)
Oil Control Ring to Groove Side Clearance ............ 0.036-0.186 mm (0.0014-0.0073 in.)
Top Compression Ring End Gap Bore ............ 0.250-0.500 mm (0.010-0.020 in.)
Center Compression Ring End Gap Bore ............ 0.250-0.510 mm (0.0010-0.020 in.)
Oil Control Ring End Gap ............ 0.250-1.020 mm (0.010-0.040 in.)
Piston Thrust Face O.D (Std) ............ 86.941-86.959 mm (3.4229-3.4236 in.)
Piston Thrust Face O.D (Maximum Wear Limit) ............ 86.814 mm (3.4179 in.)
Piston Thrust Face to Cylinder Bore Running Clearance ............ 0.041-0.044 mm (0.0016-0.0017 in.)

John Deere STX30 Engine Tightening Torque Specs

Cylinder Head ............ 20-40.7 Nm (15-30 ft-lb.)
Valve Cover ............ 10.7 Nm (7.9 ft-lb.)
Rocker Arm Screw ............ 11.3 Nm (8.4 ft-lb.)
Rocker Arm Pivot Stud Torque ............ 11.3 Nm (8.4 ft-lb.)
Connecting Rod ............ 14.7-22.7 Nm (10.9-16.8 ft-lb.)
Fuel Bowl Retaining Screw ............ 5.1-6.2 Nm (3.8-4.6 ft-lb.)
Starter Mounting Screw ............ 15.3 Nm (11.3 ft-lb.)
Flywheel Retaining Screw ............ 66.4 Nm (49 ft-lb)
Fuel Pump ............ 9.0 Nm (6.7 ft-lb.)
Spark Plug ............ 24.4-29.8 Nm (18-22 ft-lb.)
Ignition Module ............ 6.2 Nm (4.6 ft-lb.)
Muffler Retaining Nuts ............ 24.4 Nm (18 ft-lb.)
Oil Filter ............ 10.4-12.7 Nm (7.5-9.2 ft-lb.)
Oil Pan ............ 24.4 Nm (18 ft-lb.)
Oil Pump Cover ............ 6.2 Nm (4.6 ft-lb.)
Governor Control Lever ............ 9.9 Nm (7.3 ft-lb.)

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