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Home / Small Engines / Kohler Engines / Kohler CH12.5S

Kohler CH12.5S Specifications

Engine Model: Kohler Command CH12.5S

Engine Type: 4-cycle 1-cylinder air-cooled gasoline engine

Total Displacement: 24.3 cu.in (398 cc)

Rated Engine Power: 12.5 Hp (9.4 kW) at 3600 rpm

Carburetor Type: Adjustable or fixed main jet

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General Technical Data

Engine Model .............. Kohler Command CH12.5S
Engine Type .............. 4-cycle 1-cylinder horizontal shaft air-cooled gasoline engine
Number of Cylinders .............. Single
Displacement, cc (cu.in) .............. 398 (24.3)
Cylinder Bore, mm (in) .............. 87.0 (3.43)
Piston Stroke, mm (in) .............. 67.0 (2.64)
Rated Engine Power, hp (kW) .............. 12.5 (9.4)
Rated Engine Speed, rpm .............. 3600
Maximum Torque, Nm (ft-lb) .............. 27.8 (20.5)
Torque Speed, rpm .............. 2500
Idle Speed, rpm .............. 1400
Compression Ratio .............. 8.5:1
Lubrication System .............. Full pressure
Oil Filter Type .............. Full-flow
Air Cleaner Type .............. Replaceable, paper element
Ignition System .............. Electronic magneto
Starting System .............. Electric starter
Electrical System Rating, Volts .............. 12

Fuel System

Fuel System Type .............. Carburetor
Carburetor Model .............. Walbro or Nikki
Carburetor Type .............. Adjustable main jet or fixed jet
Fuel Pump Type .............. Mechanical
Fuel Filter Type .............. In-line
Governor Type .............. Mechanical

Dimensions and Weight

Overall Length, mm (in) .............. 342 (13.5)
Overall Width, mm (in) .............. 502 (19.8)
Overall Height, mm (in) .............. 440 (17.4)
Net weight, kg (lbs) .............. 40.0 (88)

Cylinder Block

Cylinder Bore Inside Diameter (Std), mm (in) .............. 87.000-87.025 (3.4252-3.4262)
Cylinder Bore Inside Diameter (Max), mm (in) .............. 87.063 (3.4277)
Cylinder Bore (Max. Out of Round), mm (in) .............. 0.12 (0.0047)
Cylinder Bore Max. Taper, mm (in) .............. 0.05 (0.0020)
Crankshaft End Play (Free), mm (in) .............. 0.0575-0.4925 (0.0022-0.0193)
Crankshaft Bore (Crankcase), mm (in) .............. 44.965-45.003 (1.7703-1.7718)
Crankshaft Bore (Closure Plate), mm (in) .............. 41.960-42.035 (1.6519-1.6549)
Crankshaft Bore to Crankshaft Clearance, mm (in) .............. 0.025-0.120 (0.00098-0.00472)
Connecting Rod to Crankpin Clearance, mm (in) .............. 0.030-0.055 (0.0012-0.0022)
Connecting Rod to Crankpin Side Clearance, mm (in) .............. 0.18-0.41 (0.007-0.016)
Connecting Rod to Piston Pin Clearance, mm (in) .............. 0.015-0.028 (0.0006-0.0011)
Connecting Rod Journal Outside Diameter, mm (in) .............. 38.958-38.970 (1.5338-1.5343)
Camshaft End Play, mm (in) .............. 0.076-0.127 (0.0030-0.0050)
Camshaft Clearance, mm (in) .............. 0.025-0.105 (0.00098-0.0041)
Camshaft Bore Inside Diameter, mm (in) .............. 20.000-20.025 (0.7874-0.7884)
Camshaft Bearing Outside Diameter, mm (in) .............. 19.962-19.975 (0.7859-0.7864)

Cylinder Head and Valves

Cylinder Head (Max Out of Flatness), mm (in) .............. 0.076 (0.003)
Hydraulic Valve Lifter to Crankcase Clearance, mm (in) .............. 0.0124-0.0501 (0.0005-0.0020)
Valve Stem to Valve Guide Clearance (Intake), mm (in) .............. 0.038-0.076 (0.0015-0.0030)
Valve Stem to Valve Guide Clearance (Exhaust), mm (in) .............. 0.050-0.088 (0.0020-0.0035)
Valve Guide Inside Diameter, mm (in) .............. 7.038-7.058 (0.2771-0.2779)
Valve Minimum Lift (Intake), mm (in) .............. 8.96 (0.353)
Valve Minimum Lift (Exhaust), mm (in) .............. 9.14 (0.360)
Valve Face Angle, degrees .............. 45
Valve Seat Angle, degrees .............. 89
Valve Insert Outside Diameter (Intake), mm (in) .............. 37.987-38.013 (1.5015-1.5024)
Valve Insert Outside Diameter (Exhaust), mm (in) .............. 34.013-33.987 (1.3443-1.3434)
Valve Guide Depth, mm (in) .............. 6.50 (0.2559)
Valve Head Diameter (Intake), mm (in) .............. 35.63-35.37 (1.4083-1.3980)
Valve Head Diameter (Exhaust), mm (in) .............. 31.63-31.37 (1.2502-1.2399)
Valve Stem Diameter (Intake), mm (in) .............. 6.982-7.000 (0.2749-0.2756)
Valve Stem Diameter (Exhaust), mm (in) .............. 6.970-6.988 (0.2744-0.2751)

Piston and Piston Rings

Piston Outside Diameter (Std), mm (in) .............. 86.941-86.959 (3.4229-3.4236)
Piston Outside Diameter (Wear Limit), mm (in) .............. 86.814 (3.4179)
Piston to Cylinder Bore Clearance, mm (in) .............. 0.041-0.044 (0.0016-0.0017)
Piston to Piston Pin Clearance, mm (in) .............. 0.006-0.017 (0.0002-0.0007)
Piston Pin Bore Inside Diameter, mm (in) .............. 19.006-19.012 (0.7483-0.7485)
Piston Pin Outside Diameter, mm (in) .............. 18.995-19.000 (0.7478-0.7480)
Top Ring Groove Clearance, mm (in) .............. 0.040-0.105 (0.0016-0.0041)
Second Ring Groove Clearance, mm (in) .............. 0.040-0.072 (0.0016-0.0028)
Oil Ring Groove Clearance, mm (in) .............. 0.551-0.675 (0.0217-0.0266)
Top Ring End Gap, mm (in) .............. 0.3-0.5 (0.012-0.020)
Second Ring End Gap, mm (in) .............. 0.3-0.5 (0.012-0.020)

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