Honda GX610 U1/R1

Honda GX610 U1, R1The Honda GX610 U1/R1 is a 614 cc (37.5 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 GX610 U1/R1 engine has an OHV (overhead valve) design with 90° V-twin cylinders; horizontal type carburetor with butterfly valve; heavy-duty recoil and electric starter, or only 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 66.0 mm (2.6 in), compression ratio rating is 8.3:1. The GX610 U1/R1 engine produced 16.9 PS (12.4 kW; 16.6 HP) of maximum horsepower at 3,600 rpm; 14.4 PS (10.6 kW; 14.2 HP) of continuous rated power at 3,600 rpm. and 39.6 N·m (4.04 kg·m, 29.2 ft·lb) of torque at 2,500 rpm.

General information

Engine Specifications
Model GX610 U1/R1
Type 4-stroke, OHV, 90° V-twin
Displacement 614 cm 3 (37.5 cu-in)
Max. horsepower 16.9 PS (12.4 kW; 16.6 HP) at 3,600 rpm
Max. torque (crank PTO) 39.6 N·m (4.04 kg·m, 29.2 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 Recoil starter or Recoil and electric starter
Stoping system Ignition primary circuit ground
Fuel used Unleaded gasoline (octane number 86 or higher)
Fuel consumption 230 g/HPh
PTO shaft rotation Counterclockwise (from PTO shaft side)

Dimensions and Weight

GX610 U1/R1
Length, mm (in) 388 (15.3)
Width, mm (in) 457 (18.0)
Height, mm (in) 452 (17.8)
Dry weight, kg (lb) 42.0 (92.6)
Operating weight, kg (lb) 43.0 (94.8)

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 GX610 U1/R1 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 Stroke 77 X 66 mm (3.0 x 2.6 in)
Sleeve internal diameter 77.00 mm (3.03 in)
Piston skirt outer diameter 76.985 mm (3.03 in)
Ring side clearance Top/Second 0.030-0.060 mm (0.0006-0.0018 in)
Ring end gap Top/Second 0.20-0.40 mm (0.010-0.020 in)
Ring width Top/Second 1.990 mm (0.0783 in)
Connecting rod small end ID 18.005 mm (0.7087 in)
Piston pin outer diameter 18.000 mm (0.7087 in)
Crankpin diameter 39.995 mm (1.5746 in)
Crankshaft journal diameter 38.000 mm (1.4961 in)
Cylinder Head
Warpage (limit) 0.10 mm (0.004 in)
Valve Arrangement: OHV
Valves: 4 (2 per cylinder)
Stem outer diameter (standard): INTAKE 6.590 mm (0.2594 in)
EXHAUST 6.550 mm (0.2579 in)
Valve spring free length: 39.0 mm (1.54 in)
Valve lifter internal diameter: 6.010 mm (0.2366 in)
Valve lifter shaft outer diameter: 6.000 mm (0.2362 in)
Camshaft journal diameter: 16.985 mm (0.6687 in)
Cam height: INTAKE 29.865 mm (1.1758 in)
EXHAUST 29.865 mm (1.1758 in)

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

Maximum speed 3,850 ± 150 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
Ignition timing 20° B.T.D.C.
Spark plug NGK: ZGR5A
Spark plug gap 0.7-0.8 mm (0.028-0.031 in)
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