Honda GV400

Honda GV400The Honda GV400 is a 406 cc (24.8 single-cylinder air-coolled 4-stroke internal combustion small gasoline engine with vertical shaft manufactured by Honda Motor Company.

The Honda GV400 engine has a slide valve (L-head) design and camshaft driven by a single row chain driven by the crankshaft. The engine has an electric or recoil starter, horizontal carburetor with butterfly valve and flywheel magneto or capacitor discharge ignition (CDI) system. The engine is equipped with dual-element air cleaner, a centrifugal governor and trochoid oil pump.

The GV400 engine a compression ratio rating is 6.5:1, cylinder bore and piston stroke are 86.0 mm (3.4 in) and 70.0 mm (2.80 in), respectively.

The Honda GV400 produced 11.0 HP (8.2 kW) at 3,600 rpm of maximum horsepower and 24.5 Nm (24.5 kg·m, 17.7 ft·lb) at 3,000 rpm of torque.


General information

Engine Specifications
Type4-stroke, side valve type (L-head), single cylinder
Displacement406 cm 3 (24.8 cu-in)
Horsepower11.0 HP (8.2 kW) at 3,600 rpm
Torque24.5 Nm (24.5 kg·m, 17.7 ft·lb) at 3,000 rpm
CarburetorHorizontal, butterfly valve
Cooling systemForced-air
Ignition systemTransistorized magneto or CDI
Lubricating systemTrochoid oil pump
Starting systemRecoil starter or electric starter
Stoping systemGround of primary circuit
Fuel usedUnleaded gasoline (octane number 86 or higher)
Fuel tank capacity2.3 L (2.43 US qt, 2.02 Imp qt.)
Fuel consumption270 g/HPh
PTO shaft rotationCounterclockwise (from PTO shaft side)

Cylinder Block and Head

The piston has two compression rings and one oil ring. Precision camshaft design offers precise valve timing and optimal valve overlap for better fuel efficiency.

Cylinder block
Compression ratio:6.5:1
Bore x Stroke86 X 70 mm (3.4 x 2.8 in)
Sleeve internal diameter86.00 mm (2.386 in)
Piston skirt outer diameter85.97-86.00 mm (3.385-3.386 in)
Number of piston rings (compression / oil):2 / 1
Ring side clearanceTop0.02-0.06 mm (0.0008-0.00024 in)
Second/oil0.01-0.05 mm (0.0004-0.0020 in)
Ring end gapTop/second0.20-0.40 mm (0.008-0.016 in)
Oil0.20-0.40 mm (0.008-0.016 in)
Connecting rod small end ID19.005-19.020 mm (0.7482-0.7488 in)
Crankshaft crank pin outer diameter36.951-36.958 mm (1.4548-1.4550 in)
Cylinder Head
Warpage (limit)0.10 mm (0.004 in)
Valve Arrangement:Side valve (L-head)
Stem outer diameter (standard):INTAKE6.955-6.970 mm (0.2738-0.2744 in)
EXHAUST6.910-6.925 mm (0.2720-0.2726 in)
Cam height:INTAKE38.5-38.7 mm (1.516-1.524 in)
EXHAUST38.5-38.7 mm (1.516-1.524 in)
Valve spring free length:42.7 mm (1.68 in)


Idle speed1700 ± 150 rpm
Cylinder compression8.0 kg/cm2 at 1400 rpm
Valve clearance
Intake valve0.06-0.12 mm (0.002-0.005 in)
Exhaust valve0.09-0.15 mm (0.004-0.006 in)
Main jet#105
Float height6.7-9.7 mm (0.26-0.38 in)
Pilot screw openingK0:1-1/2; K1:2-1/4 turns
Oil system
Oil typeHonda 4-stroke or an equivalent (SG.SF/CC.CD)
Recommended oilSAE 10W-30
Oil capacity1.2 L (2.54 US pt, 2.11 lmp pt)
Ignition system
Ignition timing20 ° B.T.D.C (Fixed)
Spark plug Flywheel magneto type: NGK: BM6A, BMR6A
Spark plug gap Flywheel magneto type: 0.6-0.7 mm (0.024-0.028 in)
CDI: 0.9-1.0 mm (0.035-0.039 in)

Tightening torque specs

Tightening torque specs
Cylinder head (10 mm bolt) Serial number before 2006140:
43-47 Nm; 4.3-4.7 kg·m; 31-40 ft·lb
Serial number after 2006141:
32-38 Nm; 3.2-3.8 kg·m; 23-27 ft·lb
Connecting rod lower cap (8 mm bolt)21-26 Nm; 2.1-2.6 kg·m; 15.6-19.1 ft·lb
Flywheel (16 mm nut)110-120 Nm; 11-12 kg·m; 77-87 ft·lb
Drain bolt (20 mm bolt)40-50 Nm; 4.0-5.0 kg·m; 29-36 ft·lb
Oil pan (8 mm bolt)21-27 Nm; 2.1-2.7 kg·m; 15-19 ft·lb
5 mm bolts, nuts4-7 Nm; 0.4-0.7 kg·m; 2.9-5.1 ft·lb
6 mm bolts, nuts8-12 Nm; 0.8-1.2 kg·m; 5.8-8.7 ft·lb
8 mm bolts, nuts20-28 Nm; 2.0-2.8 kg·m; 14.5-20.3 ft·lb
10 mm bolts, nuts35-40 Nm; 3.5-4.0 kg·m; 25-29 ft·lb
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