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Kohler CH940 Engine

The Kohler CH940 is a four-cycle V-Twin cylinder overhead valve horizontal shaft air-cooled small gasoline engine from Command PRO series. A 61.1 cubic inches (1.0 L) engine has a cylinder bore of 3.54" (90 mm), piston stroke of 3.09" (78.5 mm), and rated power of 34 Hp (25.4 kW) at 3600 rpm. The compression ratio rating is 8.8:1. The Kohler CH940 engine is equipped with a two-barrel side-draft carburetor, full pressure lubrication system, digital spark advance ignition, paper air filter, and starting system with electric starter. The operating weight is 132 lbs (59 kg).

General Technical Data

Engine Specifications

Engine Model .................. Kohler Command PRO CH940
Engine Type .................. 4-cycle V-Twin cylinder air-cooled gasoline
Number of Cylinders .................. 2
Displacement, cc (cu.in) .................. 999 (61.1)
Cylinder Bore, mm (in) .................. 90.0 (3.54)
Piston Stroke, mm (in) .................. 78.5 (3.09)
Rated Engine Power, hp (kW) .................. 34.0 (25.4)
Rated Engine Speed, rpm .................. 3600
Maximum Torque, Nm (ft-lbs) .................. 72.5 (53.5)
Torque Speed, rpm .................. 2800
Compression Ratio .................. 8.8:1
Lubrication System .................. Full pressure
Oil Filter Type .................. Full-flow type
Cooling System .................. Forced-air
Air Cleaner Type .................. Replaceable, paper element
Ignition System .................. Digital spark advance ignition
Starter Type .................. Electric
Electrical System Rating, Volts .................. 12

Fuel System

Fuel System Type .................. Carburetor
Carburetor Type .................. Two-barrel side-draft with fixed main jets
Fuel Pump Type .................. Pulse/mechanical
Fuel Filter Type .................. In-line
Governor Type .................. Mechanical

Dimensions and Weight

Overall Length, mm (in) .................. 388 (15.3)
Overall Width, mm (in) .................. 484 (19.1)
Overall Height, mm (in) .................. 700 (27.5)
Net Weight, kg (lbs) .................. 59 (132)

Maintenance Data

Engine Oil

Engine Oil Type (Summer Time) .................. SAE 10W-30, 10W-50
Engine Oil Type (Winter Time) .................. SAE 5W-30
Oil Classification (API Service) .................. SJ or higher
Oil Capacity (w/o Filter), L (qts) .................. 1.9 (2.0)
Oil Capacity (with New Filter), L (qts) .................. 2.6 (2.8)

Ignition System

Spark Plug Type .................. Champion RC12YC
Spark Plug Gap, mm (in) .................. 0.76 (0.030)
Module Air Gap, mm (in) .................. 0.28-0.33 (0.011-0.013)
Thread Size, mm (in) .................. 14 (0.55)
Spark Plug Torque, Nm (ft-lbs) .................. 27 (20)

Service Specifications

Cylinder Block

Cylinder Bore Inside Diameter (Std), mm (in) .................. 90.000-90.0025 (3.5433-3.5434)
Cylinder Bore (Max Out of Round), mm (in) .................. 0.12 (0.0047)
Crankshaft Outside Diameter, mm (in) .................. 50.00-50.025 (1.9685-1.969)
Connecting Rod Journal O.D, mm (in) .................. 35.955-35.973 (1.4156-1.4163)
Piston to Piston Pin Clearance, mm (in) .................. 0.006-0.017 (0.0002-0.0007)
Piston Pin Bore Inside Diameter, mm (in) .................. 19.006-19.013 (0.7482-0.7485)
Piston Thrust Face O.D (Std), mm (in) .................. 89.953-89.967 (3.5414-3.5420)
Piston Thrust Face O.D (Wear Limit), mm (in) .................. 89.925 (3.540)
Piston to Cylinder Bore Clearance, mm (in) .................. 0.033-0.72 (0.0013-0.0028)
Thrust Face O.D (Piston A), mm (in) .................. 89.953-89.967 (3.5414-3.542)
Piston Pin O.D (Piston A), mm (in) .................. 18.995-19.000 (0.7478-0.7480)
Top Ring Groove Clearance (Piston A), mm (in) .................. 0.040-0.080 (0.0016-0.0031)
Middle Ring Groove Clearance (Piston A), mm (in) .................. 0.040-0.080 (0.0016-0.0031)
Oil Ring Groove Clearance (Piston A), mm (in) .................. 0.030-0.190 (0.0012-0.0075)
Top Ring End Gap (Piston A), mm (in) .................. 0.300-0.550 (0.0118-0.0217)
Middle Ring End Gap (Piston A), mm (in) .................. 0.300-0.550 (0.0118-0.0217)
Thrust Face O.D (Piston B), mm (in) .................. 89.972 (3.5422)
Piston Pin O.D (Piston B), mm (in) .................. 19.995-20.000 (0.7872-0.7874)
Top Ring Groove Clearance (Piston B), mm (in) .................. 0.030-0.070 (0.001-0.0026)
Middle Ring Groove Clearance (Piston B), mm (in) .................. 0.030-0.070 (0.001-0.0026)
Oil Ring Groove Clearance (Piston B), mm (in) .................. 0.060-0.190 (0.0022-0.0073)
Top Ring End Gap (Piston B), mm (in) .................. 0.125-0.304 (0.0049-0.0120)
Middle Ring End Gap (Piston B), mm (in) .................. 0.900-1.179 (0.0345-0.0464)
Crankshaft Main Journal Diameter, mm (in) .................. 44.978-45.000 (1.7708-1.7717)
Crankpin Journal Diameter, mm (in) .................. 43.982-44.000 (1.7316-1.7323)

Cylinder Head and Valves

Cylinder Head (Max Out of Flatness), mm (in) .................. 0.076 (0.003)
Intake Valve Head Diameter, mm (in) .................. 38.625-38.685 (1.5207-1.523)
Exhaust Valve Head Diameter, mm (in) .................. 31.625-31.825 (1.2451-1.253)
Intake Valve Stem Diameter, mm (in) .................. 6.982-7.000 (0.2749-0.2756)
Exhaust Valve Stem Diameter, mm (in) .................. 6.970-6.988 (0.2744-0.2751)
Intake Valve Stem to Valve Guide Clearance, mm (in) .................. 0.038-0.076 (0.0015-0.0030)
Exhaust Valve Stem to Valve Guide Clearance, mm (in) .................. 0.050-0.088 (0.0020-0.0035)
Intake Valve Guide Inside Diameter, mm (in) .................. 7.038-7.058 (0.2771-0.2779)
Exhaust Valve Guide Inside Diameter, mm (in) .................. 7.038-7.058 (0.2771-0.2779)
Nominal Valve Face Angle, degrees .................. 45
Crankpin Journal Diameter, mm (in) .................. 43.982-44.000 (1.7316-1.7323)
Camshaft Bearing Outside Diameter, mm (in) .................. 19.962-19.975 (0.7859-0.7864)

Tightening Torque Specs

Cylinder Head Nut, Nm (ft-lb) .................. 23.7-46.9 (17.5-34.6)
Rocker Arm Screw, Nm (ft-lb) .................. 11.9 (8.7)
Connecting Rod Cap, Nm (ft-lb) .................. 11.6 (8.5)
Flywheel Retaining Screw, Nm (ft-lb) .................. 69.8 (51.1)
Intake Manifold Mounting, Nm (ft-lb) .................. 16.9 (12.5)
Carburetor Mounting Nut, Nm (ft-lb) .................. 11.3 (8.4)
Closure Plate, Nm (ft-lb) .................. 25.6 (19.1)
Oil Pump Mounting Screw, Nm (ft-lb) .................. 9.9 (7.3)
Governor Lever Nut, Nm (ft-lb) .................. 7.1 (5.3)
Ignition Module, Nm (ft-lb) .................. 4.1-9.7 (3.0-7.2)
Muffler Retaining Nut, Nm (ft-lb) .................. 24.4 (18.1)
Fan Fastener Screw, Nm (ft-lb) .................. 10.4 (7.7)
Spark Plug, Nm (ft-lb) .................. 27 (20.1)

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