Zongshen GB420S

Zongshen GB420SThe Zongshen GB420S is a 420 cc, (25.63 cu·in) natural aspirated single-cylinder four-stroke air-cooled internal combustion small gasoline engine with a horizontal shaft, manufactured by Zongshen Power Co for construction machinery, pressure washers, water pumps, outboard engines.

The Zongshen GB420S engine has a single-cylinder, overhead valve (OHV) design, and recoil or electric starter. This engine used a carburetor fuel system, transistorized magneto ignition system, splash type lubricating system, and forced-air cooling system. The GB420S engine is equipped with a 7.5 L (1.98 US. gal. 1.65 Imp. gal.) fuel tank.

The Zongshen GB420S engine produced 12.2 PS (9.0 kW; 12.1 HP) at 3,600 rpm of maximum output power and 27 N·m (2.8 kg·m, 19.9 ft·lb) of peak torque.

Engine Specifications
Engine modelGB420S
Engine type4-stroke, OHV, single-cylinder
Displacement420 cm3, (25.63 cu·in)
Max. horsepower12.2 PS (9.0 kW; 12.1 HP) at 3,600 rpm
Max. torque27 N·m (2.8 kg·m, 19.9 ft·lb)
Cooling systemForced air
Lubricating systemSplash
Ignition systemTransistorized ignition
Fuel systemCarburetor
Fuel tank capacity7.5 L (1.98 US. gal. 1.65 Imp. gal.)
Fuel usedUnleaded gasoline (octane number 86 or higher)
Starting systemRecoil or electric starter
Stoping systemIgnition primary circuit ground
PTO shaft rotationCounterclockwise (from PTO shaft side)
Dimensions (L x W X H)456 x 355 x 459 mm (18 x 14 x 18.1 in)
Dry weight30.5 kg (67.2 lbs)

Cylinder Block and Head

A 90.0 mm (3.54 in) cylinder bore and 66.0 mm (2.6 in) piston stroke give the GB420S engine a total of 420 cc of displacement.

Cylinder block
Cylinder bore:90.0 mm (3.54 in)
Piston stroke:66.0 mm (2.6 in)
Number of piston rings (compression / oil):2/1
Crankshaft center distance:33 mm (1.3 in)
Cylinder head
Valve arrangement:OHV

Service Data

Maximum speed:3,600 rpm rpm
Idle speed:1,650±200 rpm rpm
Oil system
Lubrication system:Splash
Oil type:4-stroke engine oil
Recommended oil:SAE 10W-30
Oil capacity:1.1 L (1.16 US. qt, 0.97 Imp. qt.)
Fuel system
Ignition system
Type:Transistorized ignition
Spark plug gap:0.6-0.8 mm (0.0236-0.0315 in)
Spark plug torque:20 N·m (2 kg·m, 14.7 ft·lb)
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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We try to use official documentation and verify the published data, but errors may occur. In addition, specifications of machinery and equipment may vary depending on markets and modifications. We do not recommend the use of this data for spare parts or repairs. Use official service manuals or parts catalogs for your product.

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