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Kohler CH255 Engine

The Kohler CH255 is a four-cycle single cylinder overhead valve horizontal shaft air-cooled small gasoline engine from Command PRO series. A 10.8 cubic inches (0.18 L) engine has a cylinder bore of 2.70" (68 mm), piston stroke of 1.90" (49 mm), and rated power of 5.5 Hp (4 kW) at 3600 rpm. The compression ratio rating is 8.5:1. The Kohler CH255 engine is equipped with a fixed main jet carburetor, splash lubrication system, electronic magneto ignition, paper air filter, and starting system with recoil starter. The operating weight is 33.1 lbs (15 kg).

General Technical Data

Engine Specifications

Engine Model .................. Kohler Command PRO CH255
Engine Type .................. 4-cycle OHV single cylinder air-cooled gasoline
Number of Cylinders .................. 1
Displacement, cc (cu.in) .................. 177 (10.8)
Cylinder Bore, mm (in) .................. 68.0 (2.70)
Piston Stroke, mm (in) .................. 49.0 (1.90)
Rated Engine Power, hp (kW) .................. 5.5 (4.0)
Rated Engine Speed, rpm .................. 3600
Maximum Torque, Nm (ft-lbs) .................. 8.3 (6.1)
Torque Speed, rpm .................. 2800
Compression Ratio .................. 8.5:1
Lubrication System .................. Splash type
Cooling System .................. Forced-air
Air Cleaner Type .................. Replaceable, paper element
Ignition System .................. Dependable electronic magneto
Starter Type .................. Recoil
Electrical System Rating, Volts .................. 12

Fuel System

Fuel System Type .................. Carburetor
Carburetor Type .................. Fixed main jet
Fuel Filter Type .................. In-line
Governor Type .................. Mechanical

Dimensions and Weight

Overall Length, mm (in) .................. 296 (11.6)
Overall Width, mm (in) .................. 354 (13.9)
Overall Height, mm (in) .................. 318 (12.5)
Net Weight, kg (lbs) .................. 15.0 (33.1)

Maintenance Data

Engine Oil

Engine Oil Type (Summer Time) .................. SAE 10W-30
Engine Oil Type (Winter Time) .................. SAE 5W-20, 5W-30
Engine Oil Classification (API Service) .................. SJ or higher
Engine Oil Capacity, L (qts) .................. 0.60 (0.63)

Ignition System

Spark Plug Type .................. Kohler 1413214-S
Spark Plug Gap, mm (in) .................. 0.76 (0.030)
Module Air Gap, mm (in) .................. 0.254 (0.010)
Thread Size, mm (in) .................. 14 (0.55)
Spark Plug Torque, Nm (ft-lb) .................. 27 (20)

Service Specifications

Cylinder Block

Cylinder Bore I.D (Standard) .................. 68.027-68.035 mm (2.6280-2.6785 in)
Cylinder Bore I.D (Max Out of Round) .................. 0.0127 mm (0.0005 in)
Thrust Face O.D .................. 67.975-67.985 mm (2.6762-2.6766 in)
Piston Pin O.D (Standard) .................. 17.992-17.995 mm (0.7083-0.7084 in)
Piston Pin O.D (Wear Limit) .................. 17.95 mm (0.7067 in)
Piston Pin End I.D (Standard) .................. 18.010-18.015 mm (0.7091-0.7093 in)
Piston Pin End I.D (Wear Limit) .................. 18.08 mm (0.712 in)
Top Compression Ring Groove Clearance .................. 0.040-0.150 mm (0.0020-0.0060 in)
Center Compression Ring Groove Clearance .................. 0.040-0.150 mm (0.0020-0.0060 in)
Oil Control Ring Groove Clearance .................. 0.050-0.190 mm (0.0019-0.0075 in)
Top Compression Ring End Gap .................. 0.325-0.400 mm (0.013-0.016 in)
Center Compression Ring End Gap .................. 0.325-0.400 mm (0.013-0.016 in)
Crankshaft O.D .................. 24.975-24.989 mm (0.9833-0.9838 in)
Crankshaft Main Bearing I.D .................. 24.992-25.000 mm (0.9839-0.9842 in)

Cylinder Head and Valves

Cylinder Head (Max Out of Flatness) .................. 0.08 mm (0.003 in)
Intake Valve Clearance .................. 0.0762-0.1270 mm (0.0030-0.0050 in)
Exhaust Valve Clearance .................. 0.0762-0.1270 mm (0.0030-0.0050 in)
Intake Valve Head Diameter .................. 24.875-25.125 mm (0.9793-0.9892 in)
Exhaust Valve Head Diameter .................. 23.800-24.200 mm (0.9370-0.9527 in)
Intake Valve Stem O.D (Standard) .................. 5.474 mm (0.2155 in)
Exhaust Valve Stem O.D (Standard) .................. 5.464 mm (0.2151 in)
Cam Lobe Height (Intake) .................. 27.608 mm (1.0870 in)
Cam Lobe Height (Exhaust) .................. 27.770 mm (1.0930 in)

Tightening Torque Specs

Cylinder Head Nut, Nm (ft-lb) .................. 12-24 (8.9-17.7)
Connecting Rod Screw, Nm (ft-lb) .................. 12.5 (9.1)
Flywheel Retaining Nut, Nm (ft-lb) .................. 74 (54.8)
Rocker Arm Stud, Nm (ft-lb) .................. 13.6 (10)
Ignition Module, Nm (ft-lb) .................. 10 (7.4)
Spark Plug, Nm (ft-lb) .................. 22-27 (16.3-20)
Governor Lever Nut, Nm (ft-lb) .................. 12 (8.9)
Throttle Control Lever Nut, Nm (ft-lb) .................. 9 (6.7)

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