Honda GX670

Honda GX670 engineThe Honda GX670 is a 670 cc (40.9 cu-in) V-twin cylinder air-cooled four-stroke internal combustion small gasoline engine with horizontal shaft manufactured by Honda Motor Company for general-purpose applications, such as concrete saws, pressure washers, chipper and shredders, trenchers, generators, vibratory rollers, ride-on cement trowels, lawn tractors.

The Honda GX670 engine has an OHV (overhead valve) design with 90° V-twin cylinders; horizontal type carburetor with butterfly valve; electric starter and transistorized magneto ignition system.

The 90° V-twin OHV format featuring an advanced combustion chamber design and superior intake and exhaust efficiency combines the ordinarily opposed elements of good fuel economy and high power output at the highest possible levels. An advanced breather design and three-piece oil ring improve oil circulation efficiency for lower oil consumption. The result is excellent reliability plus reduced running and maintenance costs.

The cylinder bore is 77.0 mm (3.0 in) and the piston stroke is 72.0 mm (2.8 in), compression ratio rating is 8.3:1. The GX670 engine produced 24 HP (17.7 kW HP) of horsepower at 3,600 rpm and 50.8 N·m (5.18 kg·m, 37.5 ft·lb) of torque at 2,500 rpm.

General information

Engine Specifications
ModelGX670
Type4-stroke, OHV, 90° V-twin
Displacement670 cm 3 (40.9 cu-in)
Max. horsepower24 HP (17.7 kW HP) at 3,600 rpm
Max. torque (crank PTO)50.8 N·m (5.18 kg·m, 37.5 ft·lb) at 2,500 rpm
CarburetorHorizontal type, butterfly valve
Cooling systemForced-air
Ignition systemTransistorized magneto ignition
Lubricating systemForced lubrication
Starting systemElectric starter
Stoping systemIgnition primary circuit ground
Fuel usedUnleaded gasoline (octane number 86 or higher)
Fuel consumption265 g/HPh
PTO shaft rotationCounterclockwise (from PTO shaft side)

Cylinder Block and Head

Improved crankcase rigidity, extra-durable crankshaft, and optimized cam shape reduce mechanical noise and contribute to quieter, smoother continuous operation. The Honda GX670 U/R motor equipped with high-strength sintered aluminum connecting rods to reduce weight in overlap areas and minimize vibration caused by the cylinder offset.

Cylinder block
Compression ratio:8.3:1
Bore x Stroke77 X 72 mm (3.0 x 2.8 in)
Sleeve internal diameter77.00 mm (3.03 in)
Piston skirt outer diameter76.985 mm (3.03 in)
Cylinder Head
Warpage (limit)0.10 mm (0.004 in)
Valve Arrangement:OHV
Valves:4 (2 per cylinder)

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 Information

Engine
Maximum speed3,850 ± 100 rpm
Idle speed1,400 ± 150 rpm
Cylinder compression6.0-8.0 kg/cm2 (85-114 psi) at 500 rpm
Valve clearance
Intake valve clearance0.15±0.02 mm (0.006±0.001 in)
Exhaust valve clearance0.20±0.02 mm (0.008±0.001 in)
Oil system
Oil typeHonda 4-stroke or an equivalent (SG or SF)
Recommended oilSAE 10W-30
Oil capacity1.90 L
Oil change intervalEvery 6 month or 100 Hrs.
Ignition system
Spark plugNGK: ZGR5A
DENSO: J16CR-U
Spark plug gap0.7-0.8 mm (0.028-0.031 in)
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We try to use verified sources and official documentation, however, differences between sources or errors in entering information may occur. We do not provide advice on technical issues related to the engines operation or repair. We do not recommend using provided information for engines repairing engines or spare parts ordering, use only official service manuals and spare-parts catalogs.

14 Comments

    • Hello, we are not a supplier of engines, we are only an information portal with technical specifications, so we have no any price lists.

  1. I have a gx670 v twin motor front coil fires good back one not at all bought a new coil still wont fire is there a difference in the front and back coil

  2. Hej , jeg har en Honda Gx 670 generator, den går op og ned i omdrejninger, den starter fint, men vil ikke gå op og yde max, hvad kan det skyldes, mvh Lars Friis

  3. I just bought a duck boat with a gx670 with electric srart motor. The manual shows a fuel pump attached to the motor. But it has a external inline fuel pump. Dose this mean the original fuel pump is not working?

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