GX340/390

The Next Generation of GX Engines.

With the GX340, you’re looking at one of the best engines in the business. More power. Quieter performance. Lower fuel consumption. Lower emissions. Better features. Exceptional performance. Honda’s GX series lives up to the legend, and then some.

Common Applications
  • Pressure washers
  • Commercial lawn and garden equipment
  • Tillers / cultivators
  • Generators
  • Forestry equipment
  • Construction / industrial equipment
  • Agricultural equipment
  • Small vehicles
  • Water pumps

Features

Fuel Efficient, High Output Operation
  • Digital CDI ignition system with variable timing Learn More
  • Increased compression ratio
  • Precision camshaft design offers precise valve timing and optimal valve overlap for better fuel efficency
  • OHV design for increased efficiency and optimal power transfer
Smooth Performance
  • Precision engineered components result in lower vibration
  • Ball bearing supported crankshaft for greater stability
  • Heavy duty balancer shaft
  • Improved piston design
Exceptionally Quiet
  • Large capacity, multi-chamber exhaust system
  • Improved camshaft and muffler reduce overall engine noise by up to 5 dB
  • Reduced mechanical noise due to piston design
  • Forged steel crankshaft and rigid crankcase
  • Helical cut gears
  • Sophisticated air intake system
Proven Reliability
  • Oil Alert Learn More
  • Cast iron cylinder sleeve
  • High quality materials, fit, and finish
  • Dual element air cleaner
  • Fuel Valve
  • 3-Year Limited Warranty
Easy to Use and Maintain
  • Simple throttle control
  • Large fuel tanks
  • Large automotive type fuel cap
  • Dual oil drains and fill
  • Easy, convenient, heavy duty control box
  • Easily accessible spark plug
Easy Starting
  • Heavy duty recoil starter
  • Automatic mechanical de-compression system Learn More
  • Variable ignition timing
Emissions Compliant
  • CARB and EPA certified
  • No catalyst necessary
Available Options
  • Low profile versions
  • Gear reduction options
  • Electic start
  • Spark arrester available
  • Charge and lamp coils with multiple output options available
  • Cyclone Air Cleaner available

SPECIFICATIONS

GX340

GX390

Engine Type Air-cooled 4-stroke OHV Air-cooled 4-stroke OHV
Bore x Stroke 88 X 64 mm 88 X 64 mm
Displacement 389 cm3 389 cm3
Net Power Output* 10.7 HP (8.0 kW) @ 3,600 rpm 11.7 HP (8.7 kW) @ 3,600 rpm
Net Torque 19.5 lb-ft (26.4 Nm) @ 2,500 rpm 19.5 lb-ft (26.4 Nm) @ 2,500 rpm
PTO Shaft Rotation Counterclockwise (from PTO shaft side) Counterclockwise (from PTO shaft side)
Compression Ratio 8.2:1 8.2:1
Lamp/Charge coil options 25W, 50W / 1A, 3A, 10A, 18A 25W, 50W / 1A, 3A, 10A, 18A
Carburetor Butterfly Float Type Butterfly Float Type
Ignition System Digital CDI with variable timing Digital CDI with variable timing
Starting System Recoil/electric Recoil/electric
Lubrication System Splash Splash
Governor System Centrifugal Mass Type Centrifugal Mass Type
Air Cleaner Dual element Dual element
Oil Capacity 1.16 US qt (1.1 L) 1.16 US qt (1.1 L)
Fuel Tank Capacity 6.4 U.S. qts (6.1 liters) 6.4 U.S. qts (6.1 liters)
Fuel Unleaded 86 octane or higher Unleaded 86 octane or higher
Dry Weight 69 lb (31.5 kg) 69 lb (31.5 kg)
WARNING: California Prop 65 Info

DIMENSIONS

GX340

GX390

Length (min) 16.0" (407 mm) 16.0" (407 mm)
Width (min) 19.1" (485 mm) 19.1" (485 mm)
Height (min) 17.7" (449 mm) 17.7" (449 mm)

PTO

GX340

GX390

E type Tapered shaft View Details Tapered shaft View Details
H type Reduction type PTO View Details Reduction type PTO View Details
L type Reduction type PTO View Details Reduction type PTO View Details
P type Threaded type (SAE) View Details Threaded type (SAE) View Details
Q type Straight shaft View Details Straight shaft View Details
R type Reduction type PTO View Details Reduction type PTO View Details
V type Tapered shaft View Details Tapered shaft View Details

Performance Curves

GX340 Performance Curve
GX390 Performance Curve

The SAE J1349 standard measures net horsepower with the manufacturer’s production muffler and air cleaner in place. Net horsepower more closely correlates with the power the operator will experience when using a Honda engine powered product. The power rating of the engines indicated in this document measures the net power output at 3600 rpm (7000 rpm for model GXH50, GXV50, GX25 and GX35) and net torque at 2500 rpm, as tested on a production engine. Mass production engines may vary from this value. Actual power output for the engine installed in the final machine will vary depending on numerous factors, including the operation speed of the engine in application, environmental conditions, maintenance and other variables.