The Honda GX25 is a 25 cc (1.5 cu-in) single-cylinder air-cooled four-stroke internal combustion ultra-small 360° inclinable gasoline engine manufactured by Honda Motor Company since 2002.
The Honda GX25 engine is a suitable power source for different applications like commercial lawn and garden equipment, tillers and cultivators, construction and industrial equipment, agricultural equipment, and water pumps. This engine has an OHC design with valve rocker arms and camshaft driven by a maintenance-free, low-noise timing belt, makes the engine more compact and light. It has a recoil starter, diaphragm type carburetor with the accelerator pump, transistorized magneto ignition.
The cylinder bore is 35.0 mm (1.4 in) and the piston stroke is 26.0 mm (1.0 in). The Honda GX25 mini-motor produced 1.1 PS (0.81 kW) at 7000 rpm and 1.25 Nm (0.13 kg·m, 0.94 ft·lb) at 5000 rpm.
General information
| Engine Specifications | |
| Model | GX25 |
| Type | 4-stroke, OHC, single cylinder |
| Displacement | 25 cm 3 (1.5 cu-in) |
| Max. horsepower | 1.1 PS (0.81 kW) at 7,000 rpm |
| Max. torque | 1.25 Nm (0.13 kg·m, 0.94 ft·lb) at 5,000 rpm |
| Carburetor | Diaphragm type |
| Cooling system | Forced-air |
| Ignition system | Transistorized magneto ignition |
| Lubricating system | Oil mist |
| Starting system | Recoil starter |
| Stoping system | Ignition primary circuit ground |
| Fuel used | Unleaded gasoline (octane number 86 or higher) |
| Fuel tank capacity | 0.55 L (0.14 US gal, 0.12 lmp gal) |
| Fuel consumption | 340 g/kWh (250 g/HPh, 0.55 lb/HPh) |
| PTO shaft rotation | Counterclockwise (from PTO shaft side) |
Cylinder Block and Head
| Cylinder block | ||
| Compression ratio: | 8.0:1 | |
| Bore x Stroke | 35 X 26 mm (1.4 x 1.0 in) | |
| Sleeve internal diameter | 35.00 mm (1.378 in) | |
| Piston skirt outer diameter | 34.970-34.990 mm (1.377-1.378 in) | |
| Connecting rod small end ID | 7.978-7.989 mm (0.3141-0.3145 in) | |
| Ring end gap | Top/second | 0.10-0.25 mm (0.004-0.010 in) |
| Ring width | Top/second | 0.970-0.990 mm (0.038-0.039 in) |
| Side clearance | Top/second | 0.015-0.056 mm (0.0006-0.0022 in) |
| Cylinder Head | ||
| Warpage (max) | 0.2 mm (0.01 in) | |
| Valve Arrangement: | OHV | |
| Valves: | 2 | |
| Stem outer diameter (standard): | INTAKE | 3.470-3.485 mm (0.1366-0.1372 in) |
| EXHAUST | 3.435-3.450 mm (0.1352-0.1358 in) | |
| Valve guide internal diameter | 3.50-3.52 mm (0.1378-0.1385 in) | |
| Valve spring free length | 20.66 mm (0.8134 in) | |
| Cam height: | INTAKE | 22.097 mm (0.8700 in) |
| EXHAUST | 22.097 mm (0.8700 in) | |
Tightening torque specs
| Tightening torque specs | |
| Lower crankcase | 6.4 Nm; 0.7 kg·m; 5.1 ft·lb |
| Fan cover | 6.4 Nm; 0.7 kg·m; 5.1 ft·lb |
| Reed valve plate | 3.9 Nm; 0.4 kg·m; 2.9 ft·lb |
| Ignition coil | 3.9 Nm; 0.4 kg·m; 2.9 ft·lb |
| Recoil starter pulley | 6.4 Nm; 0.7 kg·m; 4.6 ft·lb |
| Flywheel | 14.7 Nm; 1.5 kg·m; 10.8 ft·lb |
| Valve adjusting lock nut | 4.9 Nm; 0.5 kg·m; 3.6 ft·lb |
| Spark plug | 11.8 Nm; 1.2 kg·m; 8.7 ft·lb |
Maintenance data
| Engine | |
| Idle speed | 3100 ± 200 rpm |
| Cylinder compression | 9.2-11.2 kg/cm2 (131-159 psi) at 2,000 rpm |
| Valve clearance | |
| Intake valve | 0.08 ± 0.02 |
| Exhaust valve | 0.11 ± 0.02 |
| Carburetor | |
| Main jet | #35 (SAU and SAUT types) #34 (For others) |
| Oil system | |
| Oil type | Honda 4-stroke or an equivalent (SG, SF) |
| Recommended oil | SAE 10W-30 |
| Oil capacity | 0.08 L (2.7 US oz, 2.8 lmp oz) |
| Ignition system | |
| Ignition timing | 30 ° B.T.D.C (Fixed) |
| Spark plug | NGK: CMR8H |
| Spark plug gap | 0.6-0.7 mm (0.024-0.028 in) |
| Primary ignition coil resistance | 0.7-0.9 Ω |
| Secondary ignition coil resistance | 6.1-9.3 kΩ |
| Ignition coil air gap | 0.35-0.5 mm (0.014-0.020 in) |
Author:
DEAR SIR WE ARE AGRICULTURAL EQUIPMENT MANUFACTURER.
NEED DETAILED TECHNICAL SPECIFICATIONS OF HONDA GX25 FURTHER NEED TO APPROVE OUR EQUIPMENT WITH GOVT OF INDIA TEST LAB.
You are requested to provide same as much as possible.
Regards
I have a tiller with the GX25. I cannot seem to get it started. I can’t figure if the choke should be in the up or down position. In the middle it will run for about 2 seconds.
by the time I get to the switch, it stops running. Please help me!
I had the same problem, motor is on a mantis tiller. Bought the service kit for it. Kit comprises of air filter, fuel filter, spark plug, oil, gaskets .
Try the fuel filter first
replace carb 17.99 on amazone had same problem fixed it runs like new
This is the first site I’ve found that all the specs together. Thanks Guys.