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Kohler Magnum M20

General Technical Data

Kohler M20 Engine Specifications

Engine Model ........... Kohler Magnum M20/M20S
Engine Type ........... Gasoline, 4-cycle twin cylinder air-cooled
Number of Cylinders ........... 2
Displacement, cc (cu.in) ........... 769.8 (46.98)
Engine Bore, mm (in) ........... 79 (3.12)
Engine Stroke, mm (in) ........... 78 (3.06)
Rated Engine Power, hp (kW) ........... 20.0 (14.9)
Rated Engine Speed, rpm ........... 3600
Idle Speed, rpm ........... 1200
Compression ........... 6.6:1
Lubrication ........... Full pressure
Oil filter ........... Full-flow type
Air Cleaner ........... Replaceable, paper element
Ignition Type ........... Electronic
Electrical System Rating, Volts ........... 12
Starter Type ........... Electric

Fuel System

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

Dimensions

Length, mm (in) ........... 341 (13.5)
Width, mm (in) ........... 448 (17.7)
Height, mm (in) ........... 440 (17.4)
Net weight, kg (lbs) ........... 59.0 (130)

Kohler M20 Maintenance Data

Cylinder Block and Valves

Cylinder Bore I.D. (Maximum), mm (in) ........... 79.14 (3.128)
Cylinder Head (Max. Out of Flatness), mm (in) ........... 0.076 (0.003)
Intake Valve Clearance, mm (in) ........... 0.08-0.16 (0.003-0.006)
Exhaust Valve Clearance, mm (in) ........... 0.28-0.35 (0.011-0.014)

Engine Oil

Engine Oil Type (Summer Time) ........... SAE 10W-30
Engine Oil Type (Winter Time) ........... SAE 5W-20, 5W-30
Oil Classification (API) ........... SG, SH, SJ or higher.
Oil Capacity (without filter), L (qts) ........... 1.6 (1.7)
Oil Capacity (with filter), L (qts) ........... 1.4 (1.5)

Kohler Carburetor Adjustment

Main Fuel ........... 2-1/2 turns
Low Idle ........... 1 turn
Low Idle Speed, rpm ........... 1200±75
High Idle Speed, rpm ........... 3600±50

Walbro Carburetor Adjustment

Main Fuel (Fixed Jet) ........... Not adjust
Main Fuel (Adjustable Jet) ........... 1 turn
Low Idle ........... 1-1/4 turns
Low Idle Speed, rpm ........... 1200±75
High Idle Speed, rpm ........... 3600±50

Ignition System

Spark Plug Type ........... Champion RV17YC
Spark Plug Gap, mm (in) ........... 0.89 (0.035)
Module Air Gap, mm (in) ........... 0.2-0.3 (0.008-0.012)
Spark Plug Torque, Nm (ft-lbs) ........... 13.5-20.3 (10-15)

Service Intervals

Service Precleaner Element ........... Every 25 hours
Remove Cooling Shrouds and Clean Cooling Areas ........... Every 50 hours
Change Engine Oil ........... Every 50 hours
Replace Oil Filter ........... Every 50 hours
Replace Air Cleaner Element ........... Every 100 hours
Check Spark Plug Gap ........... Every 100 hours
Change Oil Filter ........... Every 200 hours
Replace Fuel Filter ........... Every 200 hours
Check Carburetor Adjustment ........... Every 200 hours
Check and Adjust Valve Clearance ........... Every 500 hours
Replace Spark Plug ........... Every 500 hours

Kohler M20 Service Specifications

Cylinder Block

Cylinder Bore Inside Diameter (Std), mm (in) ........... 79,075-79,050 (3,1255-3,1245)
Cylinder Bore Inside Diameter (Max. Wear Limit), mm (in) ........... 79,1384 (3,128)
Cylinder Bore (Max Out of Round), mm (in) ........... 0,0506 (0,002)
Cylinder Bore (Max. Taper), mm (in) ........... 0,03795 (0,0015)
Camshaft End Play, mm (in) ........... 0,0759-0,3289 (0,003-0,013)
Connecting Rod to Crankpin Clearance (Std), mm (in) ........... 0,0304-0,0608 (0,0012-0,0024)
Connecting Rod to Crankpin Clearance (Wear Limit), mm (in) ........... 0,07337 (0,0029)
Connecting Rod to Piston Pin Clearance (Std), mm (in) ........... 0,0152-0,0278 (0,0006-0,0011)
Connecting Rod Small End I.D. (Std), mm (in) ........... 18,993-19,000 (0,7507-0,7510)

Cylinder Head and Valves

Cylinder Head (Max. Out of Flatness), mm (in) ........... 0,0759 (0,003)
Valves Guide Reamer Size, mm (in) ........... 7,90625 (0,3125)
Intake Valve Tappet Clearance (Cold), mm (in) ........... 0,076-0,152 (0,003-0,006)
Exhaust Valve Tappet Clearance (Cold), mm (in) ........... 0,278-0,354 (0,011-0,014)
Intake Valve Minimum Lift (Zero Lash), mm (in) ........... 6,9322 (0,274)
Exhaust Valve Minimum Lift (Zero Lash), mm (in) ........... 6,9322 (0,274)
Intake Valve Stem O.D (Minimum), mm (in) ........... 7,85059 (0,3103)
Exhaust Valve Stem O.D (Minimum), mm (in) ........... 7,81264 (0,3088)
Nominal Valve Seat Angle (earlier), deg ........... 45
Nominal Valve Seat Angle (later), deg ........... 30
Intake Valve Guide I.D (Max. Wear), mm (in) ........... 0,1265 (0,005)
Exhaust Valve Guide I.D (Max. Wear), mm (in) ........... 0,1771 (0,007)

Piston and Piston Rings

Piston Thrust Face O.D (Std), mm (in) ........... 78,974-78,956 (3,1215-3,1208)
Piston Thrust Face O.D (Max. Wear Limits), mm (in) ........... 78,901 (3,1186)
Piston Thrust Face to Bore Clearance (Std), mm (in) ........... 0,0759-0,1189 (0,0030-0,0047)
Piston Ring End Gap (Std Bore), mm (in) ........... 0,253-0,582 (0,010-0,023)
Piston Ring End Gap (Used Bore), mm (in) ........... 0,8096 (0,032)
Max. Piston Ring Side Clearance, mm (in) ........... 0,1518 (0,006)
Piston Pin Outside Diameter, mm (in) ........... 18,972-18,978 (0,7499-0,7501)

Crankshaft

Crankshaft Main PTO and Flywheel End O.D (Std), mm (in) ........... 44,052-44,078 (1,7412-1,7422)
Crankshaft Main PTO and Flywheel End O.D (Max Wear Limit), mm (in) ........... 44,03971 (1,7407)
Crankshaft Max. Out of Round (Sleeve), mm (in) ........... 0,01265 (0,0005)
Crankshaft Max. Taper (Sleeve), mm (in) ........... 0,0253 (0,001)
Crankshaft Main Running Clearance (Max Std), mm (in) ........... 0,12397 (0,0049)
Crankshaft Main Running Clearance (Wear Limit), mm (in) ........... 0,14927 (0,0059)
Crankshaft Main New Sleeve Bearing I.D (Installed), mm (in) ........... 44,121-44,176 (1,7439-1,7461)
Crankpin O.D (Std), mm (in) ........... 37,945-37,932 (1,4998/1,4993)
Crankpin O.D (Max. Wear Limit), mm (in) ........... 37,920 (1,4988)
Crankpin (Max. Out of Round), mm (in) ........... 0,01265 (0,0005)
Crankpin (Max. Taper), mm (in) ........... 0,0253 (0,001)
Crankshaft End Play, mm (in) ........... 0,051-0,354 (0,002-0,014)

Kohler M20 Tightening Torque Specs

Cylinder Head, Nm (ft-lbs) ........... 20.3-27.1 (15-20)
Connecting Rods (New), Nm (ft-lbs) ........... 15.8 (11.7)
Connecting Rods (Used), Nm (ft-lbs) ........... 11.2 (8.3)
Flywheel Screw, Nm (ft-lbs) ........... 54.0 (40.0)
Manifold Screw/Nut, Nm (ft-lbs) ........... 16.9 (12.5)
Fuel Pump Mounting Screws, Nm (ft-lbs) ........... 4.2-5.1 (3.1-3.8)
Ignition Module, Nm (ft-lbs) ........... 3.6 (2.7)
Spark Plugs, Nm (ft-lbs) ........... 13.5-20.3 (10-15)
Oil Filter, Nm (ft-lbs) ........... 5.7-9.1 (4.2-6.7)
Closure Plate, Nm (ft-lbs) ........... 16.9 (12.5)