The Honda GX670 U/R 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 U/R 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 U/R engine produced 20.8 PS (15.3 kW; 20.5 HP) of maximum horsepower at 3,600 rpm; 19.2 PS (14.1 kW; 18.9 HP) of continuous rated power at 3,600 rpm. and 46.0 N·m (4.69 kg·m, 33.9 ft·lb) of torque at 2,500 rpm.
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General information
| Engine Specifications | |
| Model | GX670 U or R |
| Type | 4-stroke, OHV, 90° V-twin |
| Displacement | 670 cm 3 (40.9 cu-in) |
| Max. horsepower | 20.8 PS (15.3 kW; 20.5 HP) at 3,600 rpm |
| Max. torque (crank PTO) | 46.0 N·m (4.69 kg·m, 33.9 ft·lb) at 2,500 rpm |
| Carburetor | Horizontal type, butterfly valve |
| Cooling system | Forced-air |
| Ignition system | Transistorized magneto ignition |
| Lubricating system | Forced lubrication |
| Starting system | Electric starter |
| Stoping system | Ignition primary circuit ground |
| Fuel used | Unleaded gasoline (octane number 86 or higher) |
| Fuel consumption | 265 g/HPh |
| PTO shaft rotation | Counterclockwise (from PTO shaft side) |
Dimensions and Weight
| TAF | |
| Length, mm (in) | 412 (16.2) |
| Width, mm (in) | 471 (18.5) |
| Height, mm (in) | 457 (18.0) |
| Dry weight, kg (lb) | 43.5 (95.9) |
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 equipped was 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 Stroke | 77 X 72 mm (3.0 x 2.8 in) | |
| Sleeve internal diameter | 77.00 mm (3.03 in) | |
| Piston skirt outer diameter | 76.985 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 bolt | 12 Nm; 1.2 kg·m; 9 ft·lb |
| Cylinder head bolt | 34 Nm; 3.5 kg·m; 25 ft·lb |
| Socket bolt | 27 Nm; 2.7 kg·m; 20 ft·lb |
| Flywheel nut | 196 Nm; 20.0 kg·m; 145 ft·lb |
| Pivot bolt | 24 Nm; 2.4 kg·m; 17 ft·lb |
| Pivot adjusting nut | 10 Nm; 1.0 kg·m; 7 ft·lb |
| Cylinder head cover bolt | 9 Nm; 0.9 kg·m; 6.5 ft·lb |
| Oil level switch joint nut | 10 Nm; 1.0 kg·m; 7 ft·lb |
| Oil drain bolt | 39 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 speed | 3,850 ± 100 rpm |
| Idle speed | 1,400 ± 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 | |
| Oil type | Honda 4-stroke or an equivalent (SJ or later) |
| Recommended oil | SAE 10W-30 |
| Oil capacity | With oil filter: 1.40 L (1.5 US. qt, 1.2 Imp. qt.) Without oil filter: 1.10 L (1.2 US. qt, 1.0 Imp. qt.) |
| Oil change interval | Every 6 month or 100 Hrs. |
| Ignition system | |
| Spark plug | NGK: ZGR5A DENSO: J16CR-U |
| Spark plug gap | 0.7-0.8 mm (0.028-0.031 in) |
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