Honda GX670

Honda GX670The Honda GX670 is a 670 cc (40.9 cu·in) natural aspirated V-twin 90° four-stroke air-cooled internal combustion small gasoline engine with a horizontal shaft, manufactured by Honda Motor Company for general-purpose applications.

It has a 77.0 mm (3.03 in) cylinder bore and 72.0 mm (2.83 in) piston stroke. The compression ratio rating is 8.3:1.

The Honda GX670 engine produced 24.0 PS (17.7 kW; 23.7 HP) at 3,600 rpm of maximum output power and 50.8 N·m (5.2 kg·m, 37.4 ft·lb) at 2,500 rpm of peak torque.

The Honda GX670 features:

  • Overhead valve (OHV) design
  • Transistorized magneto ignition system
  • Horizontal type carburetor with butterfly valve
  • Centrifugal govervor
  • Forced lubrication system
  • Forced air cooling system
  • Recoil and electric starter or electric starter only

General information

Engine Specifications
Engine modelGX670
Engine type4-stroke, OHV, V-twin
Displacement670 cm3, (40.9 cu·in)
Max. horsepower24.0 PS (17.7 kW; 23.7 HP) at 3,600 rpm
Max. torque50.8 N·m (5.2 kg·m, 37.4 ft·lb) at 2,500 rpm
Cooling systemForced air
Air cleanerDual-element type
Lubricating systemForced lubrication
Ignition systemTransistorized magneto ignition
Fuel systemHorizontal type carburetor with butterfly valve
Fuel consumption265 g/HPh
Fuel tank capacity
Fuel usedUnleaded gasoline (octane number 86 or higher)
Starting systemRecoil and electric starter or electric starter on
Stoping systemIgnition primary circuit ground
GovernorCentrifugal govervor
PTO shaft rotationCounterclockwise (from PTO shaft side)
Dimensions (L x W X H)
Dry weight

Cylinder Block and Head

Cylinder block
Compression ratio:8.3:1
Cylinder bore:77.0 mm (3.03 in)
Piston stroke:72.0 mm (2.83 in)
Cylinder internal diameter (standard):77.000 mm (3.0315 in)
Piston skirt outer diameter (standard):76.985 mm (3.0309 in)
Number of piston rings (compression / oil):2/1
Crankshaft center distance:36 mm (1.415 in)
Cylinder head
Valve arrangement:OHV
Valves:2 (4 valves in total)

Tightening torque specs

Tightening torque specs
Connecting rod bolt12 Nm; 1.2 kg·m; 9 ft·lb
Cylinder head bolt34 Nm; 3.5 kg·m; 25 ft·lb
Socket bolt27 Nm; 2.7 kg·m; 20 ft·lb
Flywheel nut196 Nm; 20.0 kg·m; 145 ft·lb
Pivot bolt24 Nm; 2.4 kg·m; 17 ft·lb
Pivot adjusting nut10 Nm; 1.0 kg·m; 7 ft·lb
Cylinder head cover bolt9 Nm; 0.9 kg·m; 6.5 ft·lb
Oil level switch joint nut10 Nm; 1.0 kg·m; 7 ft·lb
Oil drain bolt39 Nm; 4.0 kg·m; 29 ft·lb
Standard torque values
Bolt, nut (5 mm)5.5 Nm; 0.55 kg·m; 4.0 ft·lb
Bolt, nut (6 mm)10 Nm; 1.0 kg·m; 7 ft·lb
Bolt, nut (8 mm)22 Nm; 2.2 kg·m; 16 ft·lb
Bolt, nut (10 mm)34 Nm; 3.5 kg·m; 25 ft·lb
Bolt, nut (12 mm)54 Nm; 5.5 kg·m; 40 ft·lb

Service Data

Maximum speed:3,850±150 rpm
Idle speed:1,450±150 rpm
Cylinder compression:6.0-8.0 kg/cm2 (85-114 psi) at 500 rpm
Valve clearance
Intake valve clearance:0.15±0.02 mm (0.006±0.001 in)
Exhaust valve clearance:0.20±0.02 mm (0.008±0.001 in)
Oil system
Lubrication system:Forced lubrication
Oil type:Honda 4-stroke or an equivalent (SJ or later)
Recommended oil:SAE 10W-30
Oil capacity: W/out oil filter: 1.5 L (1.6 US.qts, 1.32 Imp. qts)
With oil filter: 1.8 L (1.9 US.qts, 1.6 Imp. qts)
Fuel system
Type:Horizontal type carburetor with butterfly valve
Ignition system
Type:Transistorized magneto ignition
Spark plug:NGK ZGR5A DENSO J16CR-U
Spark plug gap:0.7-0.8 mm (0.0276-0.0315 in)
Author: Sergei Wers
About: Co-founder and CEO of a multi-brand auto repair shop (engine repair, chassis repair, body repair and painting) for over 15 years. I have been developing internet sites with technical specifications for more than seven years.

ATTENTION! Dear visitors, this is an informational database of technical specifications, we are not a parts supplier or a marketplace.

We try to use official documentation and verify the published data, but errors may occur. In addition, specifications of machinery and equipment may vary depending on markets and modifications. We do not recommend the use of this data for spare parts or repairs. Use official service manuals or parts catalogs for your product.

1 Comment

  1. Bought an old gx67o Honda engine i am trying to order replacement parts for but with the output shaft size of 36.7mm.. Is this engine still in production today and how or where can I get parts for it.

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