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Honda Engines GX390 Series General Purpose Straight Shaft Engine 390 ccm, 3 31/64 x 1, Tapped 3/8 24 UNF GX390UTIQA2

  • Honda GX390
  • Honda GX390-
  • Honda GX390- BlackMax Generator
  • Honda GX390- Simpson WaterBlaster Pressure Washer
  • Honda GX390- Northern Hydraulics Big Red Power Pack
  • Honda GX390- BeeLine Stump Grinder
  • Honda GX390- Digital CDI Ignition Coil
  • Honda GX390- GX series engines offer premium features and quality
  • Honda GX390- Superior air filtration systems
  • Honda GX390- Ball bearing supported crankshaft
  • Honda GX390- Dual oil drains and fill
  • Honda GX390- Automatic mechanical decompression for easier starting
  • Honda GX390- Multiple charging coil options
78.00 LBS
Calculated at checkout

Product Description

The GX390 is all new for 2010, featuring more power, quieter performance, lower fuel consumption, and lower emissions. With new features and better performance, the new GX engines establish themselves yet again as the best engines in the business.

Common Applications

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

Fuel Efficient, High Output Operation

  • Digital CDI ignition system with variable timing
  • Increased compression ratio
  • Precision camshaft design offers precise valve timing and optimal valve overlap for better fuel efficiency
  • 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
  • Forged steel crankshaft and rigid crankcase
  • Helical cut gears
  • Sophisticated air intake system

Proven Reliability

  • Oil Alert
  • 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
  • Variable ignition timing

Emissions Compliant

  • CARB and EPA certified
  • No catalyst necessary

Available Options

  • Low profile versions
  • Gear reduction options
  • Electric start
  • Spark arrester available
  • Charge and lamp coils with multiple output options available
  • Cyclone Air Cleaner available


  • Tapped 3/8 24 UNF

Engine Type

Air-cooled 4-stroke OHV

Bore x Stroke

88 X 64 mm


389 cm3

Net Power Output*

11.7 HP (8.7 kW) @ 3,600 rpm

Net Torque

19.5 lb-ft (26.4 Nm) @ 2,500 rpm

PTO Shaft Rotation

Counterclockwise (from PTO shaft side)

Compression Ratio


Lamp/Charge coil options

25W, 50W / 1A, 3A, 10A, 18A


Butterfly Float Type

Ignition System

Digital CDI with variable timing

Starting System


Lubrication System


Governor System

Centrifugal Mass Type

Air cleaner

Dual element

Oil Capacity

1.16 US qt (1.1 L)

Fuel Tank Capacity

6.4 U.S. qts (6.1 liters)


Unleaded 86 octane or higher

Dry Weight

69 lb (31.5 kg)


Length (min)

16.0" (407 mm)

Width (min)

19.1" (485 mm)

Height (min)

17.7" (449 mm)

PTO Shaft Options

E type

Tapered shaft

H type

Reduction type PTO

L type

Reduction type PTO

P type

Threaded type (SAE)

Q type

Straight shaft

R type

Reduction type PTO

V type

Tapered shaft

*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.


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