Honda GD1250

Honda GD1250 diesel engineThe Honda GD1250 is a 1.25 l (1,235 cc, 75.6 cu-in) three-cylinder water-cooled 4-stroke diesel engine, manufactured by Honda Motor Company for general-purpose applications.

An 82 mm (3.23 in) cylinder bore and 78 mm (3.07 in) piston stroke give the engine a total of 1,235 cc (75.6 cu-in) of displacement. Compression ratio rating is 18:1.

It produced up to 24 HP (16.4 kW) of maximum output (modification SH3). The maximum torque is 55.9 N·m (5.7 kg·m, 41.22 ft·lb) at 2,200 rpm.

General information

Engine Specifications
Type4-stroke, OHV, three cylinder
Displacement1,235 cm 3 (75.6 cu-in)
Max. horsepower SH1: 20 HP (14.9 kW) at 2,600 rpm
SH2: 22 HP (16.4 kW) at 3,000 rpm
SH3: 24 HP (17.9 kW) at 3,600 rpm
Max. torque (crank PTO) SH1: 64.7 N·m (6.6 kg·m, 47.73 ft·lb) at 2,600 rpm
SH2: 61.8 N·m (6.3 kg·m, 45.56 ft·lb) at 2,000 rpm
SH3: 55.9 N·m (5.7 kg·m, 41.22 ft·lb) at 2,200 rpm
Firing order1-3-2 (1-2-3 from timing belt side)
Injection timing SH1, SH2: B.T.D.C 15°
SH3: B.T.D.C 18°
Cooling systemLiquid-cooling
Lubricating systemForced oil by trochoid pump
Starting systemStarter motor
Fuel usedDiesel fuel
Fuel tank capacity20.0 l (5.28 US. Gal, 4.40 Imp. Gal.)
Fuel consumption SH1: 180 g/psh (18 HP/2,600 prm)
SH2: 194 g/psh (20 HP/3,000 prm)
SH3: 214 g/psh (22 HP/3,600 prm)
PTO shaft rotationCounterclockwise (from PTO shaft side)

Dimensions and Weight

Length, mm (in)520 (20.5)
Width, mm (in)415 (16.3)
Height, mm (in)540 (21.3)555 (21.9)
Dry weight, kg (lb)100.0 (220.5)

Cylinder Block and Head

Cylinder block
Compression ratio:18:1
Bore x Stroke82 mm X 78 mm (2.99 x 3.07 in)
Sleeve internal diameter82.000-82.017 mm (3.2283-3.2290 in)
Piston skirt outer diameter81.930-81.950 mm (3.225-3.226 in)
Number of piston rings (compression / oil):2 / 1
Ring side clearanceTop0.085-0.115 mm (0.0033-0.0045 in)
Second0.055-0.085 mm (0.0022-0.0022 in)
Oil0.020-0.055 mm (0.0008-0.0022 in)
Ring end gapTop0.20-0.40 mm (0.008-0.016 in)
Second0.20-0.40 mm (0.008-0.016 in)
Oil0.20-0.40 mm (0.008-0.016 in)
Piston pin outer diameter22.994-23.000 mm (0.9053-0.9055 in)
Connecting rod small end ID23.010-23.028 mm (0.9060-0.9066 in)
Cylinder Head
Distortion of cylinder head0.05 mm (0.002 in)
Valve Arrangement:OHV
Stem outer diameter (standard):INTAKE6.575-6.590 mm (0.2589-0.2594 in)
EXHAUST6.545-6.560 mm (0.2577-0.2583 in)
Guide internal diameterINTAKE / EXHAUST6.600-6.615 mm (0.2598-0.2604 in)
Spring free length38.1 mm (1.33 in)
Cam lobe heightINTAKE / EXHAUST39.538-39.938 mm (1.5566-1.5724 in)
Valve rocker arm internal diameter16.012-16.030 mm (0.6304-0.6311 in)
Rocker arm shaft outer diameter15.976-16.994 mm (0.6290-0.6691 in)

Tightening torque specs

Tightening torque specs
Camshaft holder bolts22 Nm; 2.2 kg·m; 16 ft·lb
Head cover nuts10 Nm; 1.0 kg·m; 7 ft·lb
Cylinder head bolts (M12) Step 1: 45 Nm; 4.5 kg·m; 32 ft·lb
Step 2: Turn all bolts 90°
Step 3: Turn all bolts 90° once more
Cylinder head bolts (M8)30 Nm; 3.0 kg·m; 22 ft·lb
Timing belt driven pulley bolt38 Nm; 3.8 kg·m; 27 ft·lb
Timing belt adjuster bolt43 Nm; 4.3 kg·m; 31 ft·lb
Crankshaft bearing cap bolts68 Nm; 6.8 kg·m; 49 ft·lb
Connecting rod cap nuts32 Nm; 3.2 kg·m; 23 ft·lb
Rear end plate bolts55 Nm; 5.5 kg·m; 40 ft·lb
Flywheel bolts115 Nm; 11.5 kg·m; 83 ft·lb
Flywheel housing55 Nm; 5.5 kg·m; 40 ft·lb
Oil filter holder55 Nm; 5.5 kg·m; 40 ft·lb
Oil filter cartridge22 Nm; 2.2 kg·m; 16 ft·lb
Fuel pipe nuts22.5 Nm; 2.25 kg·m; 16.3 ft·lb
Fuel joint bolts22.5 Nm; 2.25 kg·m; 16.3 ft·lb
Injection nozzle nuts Step 1: 5 Nm; 0.5 kg·m; 3.6 ft·lb
Step 2:10 Nm; 1.0 kg·m; 7 ft·lb
Governor shaft43 Nm; 4.3 kg·m; 31 ft·lb
Glow plugs17.5 Nm; 1.75 kg·m; 12.7 ft·lb
Glow plug nuts1.25 Nm; 0.125 kg·m; 0.9 ft·lb
Injection pump nut and bolts22 Nm; 2.2 kg·m; 16 ft·lb
Oil pressure switch20 Nm; 2.0 kg·m; 14 ft·lb
Drain plug bolt45 Nm; 4.5 kg·m; 32 ft·lb
Thermostat switch22.5 Nm; 2.25 kg·m; 16.3 ft·lb
Crankshaft pulley115 Nm; 11.5 kg·m; 83 ft·lb

Service Information

Maximum speed SH1: 2,750 rpm
SH2: 3,120 rpm
SH3: 3,740 rpm
Idle speed800 rpm
Cylinder compression27.0 kg/cm2 (384 psi) at 200 rpm
Valve clearance
Intake valve0.20 ± 0.02 (0.006 ± 0.00078)
Exhaust valve0.20 ± 0.02 (0.006 ± 0.00078)
Oil system
Oil typeDiesel oil (API Service Classification CC or CD)
Recommended oilSAE 10W-30
Oil capacity SH1: 2.9 l (3.07 US. qt, 2.55 Imp. qt.)
SH2, SH3: 4.8 l (5.07 US. qt, 4.22 Imp. qt.)
Oil pressure4.0 kg/cm2 (57 psi) at 800 rpm
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.

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