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Honda G-100 Engine

General Technical Data

Honda G100 Engine Specifications

Engine Model ................. Honda G100
Engine Type ................. 4-cycle side valve 1-cylinder air-cooled small gasoline engine
Number of Cylinders ................. Single
Displacement (G100K1), cu.in (cc) ................. 5.06 (83)
Displacement (G100K2), cu.in (cc) ................. 6.00 (98)
Engine Bore (G100K1), in (mm) ................. 1.89 (48.0)
Engine Bore (G100K2), in (mm) ................. 2.06 (52.0)
Engine Stroke, in (mm) ................. 1.82 (46.0)
Rated Engine Power (G100K1), hp (kW) ................. 2.2 (1.64)
Rated Engine Power (G100K2), hp (kW) ................. 2.5 (1.85)
Rated Engine Speed, rpm ................. 4200
Maximum Torque (G100K1), Nm (ft-lbs) ................. 3.3 (2.4)
Maximum Torque (G100K2), Nm (ft-lbs) ................. 3.5 (2.5)
Torque Speed, rpm ................. 3000
Compression ................. 6.5:1
PTO Shaft Rotation ................. Counterclockwise (from PTO shaft side)
Valve Arrangement ................. L-head
Lubrication System ................. Splash type
Air Cleaner ................. Oil bath
Cooling System ................. Forced air
Ignition System ................. Flywheel magneto
Starter Type ................. Recoil

Fuel System

Fuel System Type ................. Carburetor
Carburetor Type ................. Horizontal with butterfly valve
Fuel Consumption, g/HPh ................. 320
Fuel Tank Capacity, qts (L) ................. 1.5 (1.4)
Fuel Type ................. Gasoline (66 or higher)

Dimensions and Weight

Length, in (mm) ................. 10.8 (275)
Width, in (mm) ................. 10.6 (270)
Height, in (mm) ................. 13.6 (345)
Net Weight, lbs (kg) ................. 19.2 (8.7)

Honda G100 Maintenance Data

Cylinder Block and Valves

Cylinder Bore Inside Diameter (G100K1, Maximum), in (mm) ................. 1.8985 (48.055)
Cylinder Bore Inside Diameter (G100K2, Maximum), in (mm) ................. 2.0577 (52.060)
Cylinder Head (Max. Out of Flatness), in (mm) ................. 0.004 (0.10)
Intake Valve Clearance, in (mm) ................. 0.0031-0.0063 (0.08-0.16)
Exhaust Valve Clearance, in (mm) ................. 0.0031-0.0063 (0.08-0.16)

Engine Oil

Engine Oil Type (Summer) ................. SAE 10W-30, 10W-40
Engine Oil Type (Winter) ................. SAE 10W
API Service Classifications ................. SJ
Oil Capacity, qts (L) ................. 0.48 (0.45)

Carburetor Adjustment

Main Jet ................. #62
Idle Fuel ................. 2 turns out
Float Height, in (mm) ................. 0.42-0.53 (10.7-13.3)
Low Idle Speed, rpm ................. 1400±100
High Idle Speed, rpm ................. 3850±100

Ignition System

Spark Plug Type ................. NGK BM4A, BMR4A
Spark Plug Gap, in (mm) ................. 0.0236-0.0276 (0.60-0.70)
Module Air Gap, in (mm) ................. 0.008-0.024 (0.20-0.60)
Ignition Timing, deg ................. 20 BTDC
Spark Plug Torque, Nm (ft-lbs) ................. 20 (14)

Service Intervals

Service Air Cleaner ................. Every 50 hours
Change Engine Oil ................. Every 100 hours
Clean Fuel Strainer ................. Every 100 hours
Check and Service Spark Plug ................. Every 100 hours
Clean Sediment Cup ................. Every 100 hours
Check Ignition Timing ................. Every 150 hours
Replace Spark Plug ................. Every 200 hours
Check and Adjust Carburetor ................. Every 200 hours
Check and Adjust Valve Clearance ................. Every 200 hours

Honda G100 Service Specifications

Cylinder Block

Cylinder Compression, psi (kPa) ................. 92.5 (637)
Cylinder Bore Inside Diameter (G100K1, Std), in (mm) ................. 1.89 (48.00)
Cylinder Bore Inside Diameter (G100K1, Wear Limit), in (mm) ................. 1.8985 (48.055)
Cylinder Bore Inside Diameter (G100K2, Std), in (mm) ................. 2.06 (52.00)
Cylinder Bore Inside Diameter (G100K2, Wear Limit), in (mm) ................. 2.0577 (52.060)
Piston Skirt Outside Diameter (G100K1), in (mm) ................. 1.8503 (47.995)
Piston Skirt Outside Diameter (G100K2), in (mm) ................. 2.0549 (51.990)
Connecting Rod Small End Inside Diameter (Std), in (mm) ................. 0.393 (10.00)
Connecting Rod Small End Inside Diameter (Wear Limit), in (mm) ................. 0.397 (10.05)
Connecting Rod Big End Inside Diameter (Std), in (mm) ................. 0.708 (18.00)
Connecting Rod Big End Inside Diameter (Wear Limit), in (mm) ................. 0.713 (18.04)
Crank Pin Outside Diameter, in (mm) ................. 0.707 (17.98)
Top Compression Ring to Groove Side Clearance, in (mm) ................. 0.0004-0.002 (0.01-0.05)
Second Compression Ring to Groove Side Clearance, in (mm) ................. 0.0004-0.002 (0.01-0.05)
Oil Ring to Groove Side Clearance, in (mm) ................. 0.0004-0.002 (0.01-0.05)
Top Compression Ring End Gap, in (mm) ................. 0.009 (0.25)
Second Compression Ring End Gap, in (mm) ................. 0.009 (0.25)
Oil Ring End Gap, in (mm) ................. 0.017 (0.45)

Cylinder Head and Valves

Number of Valves ................. 2
Cylinder Head (Max. Out of Flatness), in (mm) ................. 0.004 (0.10)
Intake Valve Clearance, in (mm) ................. 0.0031-0.0063 (0.08-0.16)
Exhaust Valve Clearance, in (mm) ................. 0.0031-0.0063 (0.08-0.16)
Intake Valve Stem Outside Diameter (Std), in (mm) ................. 0.2161 (5.490)
Intake Valve Stem Outside Diameter (Wear Limit), in (mm) ................. 0.2154 (5.450)
Exhaust Valve Stem Outside Diameter (Std), in (mm) ................. 0.2143 (5.445)
Exhaust Valve Stem Outside Diameter (Wear Limit), in (mm) ................. 0.2134 (5.40)
Valve Guide Inside Diameter (Intake/Exhaust), in (mm) ................. 0.2165 (5.50)
Valve Spring Free Length, in (mm) ................. 1.066 (27.10)
Valve Seat Width (Intake/Exhaust), in (mm) ................. 0.028 (0.70)
Camshaft Journal Diameter, in (mm) ................. 0.4796 (12.184)

Honda G100 Tightening Torque Specs

Carburetor, Nm (ft-lb) ................. 4-6 (2.9-4.3)
Flywheel Nut, Nm (ft-lb) ................. 45-55 (32.5-40)
Governor Arm Nut, Nm (ft-lb) ................. 8-12 (5.8-8.7)
Cylinder Head Cover Bolt, Nm (ft-lb) ................. 8-12 (5.8-8.7)
Crankcase Cover, Nm (ft-lb) ................. 8-12 (5.8-8.7)
Connecting Rod Bolt, Nm (ft-lb) ................. 4-6 (2.9-4.3)
Spark Plug, Nm (ft-lb) ................. 18-20 (12-14)