Gx390 race engine

Gx390 race engine DEFAULT




Engine TypeAir-cooled 4-stroke OHVAir-cooled 4-stroke OHV
Bore x Stroke88 X 64 mm88 X 64 mm
Displacement389 cm3389 cm3
Net Power Output*10.7 hp (8.0 kW) @ 3,600 rpm11.7 hp (8.7 kW) @ 3,600 rpm
Net Torque19.5 lb-ft (26.4 Nm) @ 2,500 rpm19.5 lb-ft (26.5 Nm) @ 2,500 rpm
PTO Shaft RotationCounterclockwise (from PTO shaft side)Counterclockwise (from PTO shaft side)
Compression Ratio8.2:18.2:1
Lamp/Charge coil options25W, 50W / 1A, 3A, 10A, 18A25W, 50W / 1A, 3A, 10A, 18A
CarburetorButterfly Float TypeButterfly Float Type
Ignition SystemDigital CDI with variable timingDigital CDI with variable timing
Starting SystemRecoil/electricRecoil/electric
Lubrication SystemSplashSplash
Governor SystemCentrifugal Mass TypeCentrifugal Mass Type
Air CleanerDual elementDual element
Oil Capacity1.16 US qt (1.1 L)1.16 US qt (1.1 L)
Fuel Tank Capacity6.4 U.S. qts (6.1 liters)6.4 U.S. qts (6.1 liters)
FuelUnleaded 86 octane or higherUnleaded 86 octane or higher
Dry Weight69 lb (31.5 kg)69 lb (31.5 kg)
WARNING: California Prop 65 Info



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)


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.


General Applications


General Applications

Internal Combustion Engine Products:

WARNING: This product can expose you to chemicals including soots, tars, and mineral oils, which are known to the State of California to cause cancer, and carbon monoxide, which is known to the State of California to cause birth defects or other reproductive harm.

For more information go to www.P65Warnings.ca.gov.

Honda’s Auto Choke System This user-friendly system is truly automatic, eliminating any manual manipulation of levers.

The engine starts easily whether cold or hot and is ready to use immediately. Once the engine is up and running, the Auto Choke automatically returns to an optimal operating position.

All engines

Honda’s automatic mechanical decompression system is designed to give you quicker, easier starts.

This system, which is connected to the camshaft, reduces compression by opening the exhaust valve slightly when the engine is being started.  This reduces the amount of force needed to start the engine and improves starting performance.

The system disengages automatically after the engine starts to prevent any power loss during normal operation.

Mini 4-Stroke Series

In addition to the milder operating noise of 4-Stroke engines in general, the Mini 4-Stroke’s belt-driven OHC design further reduces unpleasant mechanical noise.   Its lighter piston and other moving parts help keep vibration to a comfortable level.

SAE J1939 CAN Bus (Controller Area Network) communication functionality provides ECU (Electronic Control Unit) connectivity with less wiring. It enables a variety of complicated electronic controls to be linked to improve operability.

GC series, GS series

A truly innovative combination of a compact combustion chamber, overhead cam configuration and uniblock construction significantly reduces fuel and oil consumption as compared to conventional side-valve engines.

Honda’s simple design has made the GC and GS Series lighter and more compact than any engine in their class. Plus, simple construction has minimized the number of parts, making the engine more reliable and easier to operate.

SAE J1939 CAN Bus (Controller Area Network) communication functionality provides ECU (Electronic Control Unit) connectivity with less wiring. It enables a variety of complicated electronic controls to be linked to improve operability.

Honda Cycloflow™ technology enhances the air-fuel mixture and makes it easier to start the engine and idle smoothly while making it more resilient to poor quality fuel.

New V-shaped valves and a pent-roof combustion chamber enable air in cylinder to flow more smoothly and maximizes the mixing of fuel. The longer stroke design also enhances turbulence in the cylinder, helping the mixture of air and fuel.

Drive-By-Wire unlike conventional models, has no throttle cable. An ECU controls a throttle motor via an electrical signal. Ideal throttle control is possible, from conventional type user-operated throttle control, to a variety of automatic control by the ECU.

Electronic Fuel Injection (EFI), which detects the state of the engine using sensors supplies the optimum amount of fuel to the engine according to its working conditions. EFI Improves fuel economy, reduces exhaust gas, and achieves excellent usability and easy maintenance.

Electronic Fuel Injection eliminates the need for a manual choke, making starting simple. In addition, starting is improved as the fuel is sealed within the injector and fuel hose reducing fuel deterioration, and making smooth engine startup possible even after long-term storage.

iGX Series

The electronic governor minimizes governor droop.  This increases available power.

For most normal engines, available power is decreased when the engine is approaching wide open throttle.

The iGX’s advanced electronic governor eliminates this by electronically controlling the throttle to achieve a higher effective power output.

Engine diagnosis utilizes Dr. H. software, linked via USB to tablet or PC for quick repairs.

The new integrated Fuel-Off position on the engine control allows the user to stop the flow of fuel to the engine when pressure washing is complete.

How does it work - With the engine running and the switch placed in the Fuel-Off position, the fuel flow to the carburetor is stopped. The engine will continue to run until the majority of fuel remaining in the carburetor is consumed and the engine shuts down.

Using the Fuel Off feature when shutting your pressure washer down helps prevent sticky carburetor buildup which makes for cleaner storage and easier future starting.

Mini 4-Stroke Series

The innovative design of Honda’s Mini 4-Stroke engines allows them to be used and stored in any position for full 360° usability. Upright, sideways, even upside down – the Mini 4-Strokes will still run great.

An exclusive Honda rotary-slinger lubrication system keeps oil in a completely misted state and circulates it using pressure fluctuations generated by the movement of the piston.

Built-in passages effectively return the circulated oil to the oil reservoir from every part of the engine.  An oil return port positioned in the center of the reservoir prevents oil from accidentally flowing into the combustion chamber.

Mini 4-Stroke Series

Efficient 4-Stroke technology not only offers superior fuel economy, it also requires no mixing of oil in the engine’s fuel supply.  This substantially reduces both oil consumption and the emission of unburned oil in the exhaust.

The results include better all-around environmental performance and operating costs that actually decrease the more the engine is used!

V-twin Series

Honda’s hemispherical combustion chamber was inspired by our proven racing technology.  It offers the highest V-Twin compression ratio on the market.

The power is transmitted through forged-steel connecting rods and a forged-steel crankshaft, supported by a full-pressure lubrication system.

  • 9.3:1 compression ratio generates tremendous power.
  • Excellent combustion efficiency.
  • Allows a radial configuration to create high volumetric efficiency.
  • Places the spark plug near the center of the chamber for optimal flame travel.

This means increased engine efficiency and more power to your application.

V-Twin Series

The lubrication system uses a high capacity pump with discrete chambers.  This facilitates consistent oil delivery.

The high output oil pump offers numerous benefits:

  • Twice the capacity of the previous model
  • Redesigned pump cover and sealing system ensure engine reliability
  • Full pressure lubrication to the flywheel, PTO, and connecting-rod bearings

The result?

  • Reduced friction
  • Extended engine life
  • Less mechanical engine noise
V-twin Series

The idea of integrating the cylinder & head into one unit is radical. Radically smart. It eliminates the head gasket, head bolts, and allows for more airflow and better cooling.

Speaking of cooling, improved cooling means better combustion management. Cooling is also improved by each of the lightweight aluminum pushrods being housed in a separate tube to achieve enhanced airflow.

When you put it all together (with fewer parts) you get an engine with reduced emissions and greater-than-ever durability.

iGX Series

Honda iGX engines feature an integrated ECU (electronic control unit) with a self-tuning regulator (STR) governor system.

The innovative ECU monitors and controls engine functions including Throttle, Choke, Ignition Timing, and Oil Alert.  On some models, it also offers programmable governor and throttle modes for unprecedented flexibility.  A diagnostic LED helps with trouble shooting.  Stepper motors precisely control throttle and choke position.

This allows the engine to communicate with the machine it is powering.

  • Operation is automated
  • Control becomes surer, faster and easier.
  • Enables drive-by-wire remote control operation of the engine, regulating functions such as starting, throttle, ignition timing and diagnostics.
  • Engine speed can be programmed and varied based on the equipment application's load and speed requirement.
  • Easier for inexperienced users to operate
  • Easily maintained - Ideal for rental applications

Control panel mounted LED indicator informs the user about potential problems using 10 different trouble codes. The indicator is designed to stop the engine, or alert the operator of potential issues, helping to protect and extend engine life.

GC series, GS series

Honda’s GC and GS engines use the world’s first small engine internal timing belt, designed to last the lifetime of the engine.

Small engine timing belts are usually external and are subject to wear caused by dirt.  Honda’s internal timing belt runs in oil, eliminating the need for conventional drive gears. 

This design:

  • Improves lubrication,
  • Reduces the weight of the engine, and
  • Provides quieter operation.
GX series, V-twin series, iGX series

Honda’s Oil Alert system helps to prevent engine seizure due to a low oil condition.

The system consists of an oil level sensor inside the crankcase.  When the oil reaches a level that is too low for safe operation, the engine warns you or stops automatically. 

Honda’s All-New GCV pressure washer engines offer an overhead valve (OHV) layout. The OHV design, new V-shaped valves and a pent-roof shape of combustion chamber enable air in cylinder to flow more smoothly increasing combustion efficiency, allowing for higher compression ratios and greater power output.

The OHV layout, with enhanced valve positioning and combustion chamber, the new GCV170 pumps out an increase in torque of 18 percent and a nine percent horsepower gain over the GCV160; GCV200: also showed a strong increase in torque of 13 percent and 10 percent horsepower gain over the GCV190

STR Governor (Self Tuning Regulator) minimizes engine droop seen with traditional mechanical governor systems by electronically regulating the throttle opening to maintain constant, stable engine speed even under changing load conditions, resulting in exceptional performance and enhanced user satisfaction.

GX240-390, V-Twin series, iGX series

Honda’s Variable Timing Digital CDI ignition allows optimal ignition timing based on engine speed. The result:

  • Excellent starting,
  • High power output,
  • Reduced fuel consumption, and
  • Outstanding emissions performance.

An engine rev limiter is also incorporated to prevent over-revving.

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2021 © American Honda Motor Co., Inc. All information contained herein applies to U.S. products only.

Sours: https://engines.honda.com/models/model-detail/x-large-gx

Engine, 460cc, Racing Engine - Barebones Builder Kit

These engines are custom made to our specifications and are the only 458cc Honda GX390 "big bore clones" available for purchase in Europe.

This kit doesn't include Piston, rings, rod, cam, valvetrain, pull starter or balance shaft. If you need those pieces, we do sell them individually.

-Heavy Duty 10-Bolt Engine Block (Modified Extra-Thick & Reinforced Casting) - The strongest clone engine block on the market!
-92mm Bore x 69mm Stroke
-Uses all GX390 Performance Parts (Cams, Valvetrain, etc)
-Available with or without Electric Starter

The builder kits are designed for those who are experienced builders/racers and/or building an open motor in which many of the stock components will not be used.

Why throw away the stock parts when you dont have to buy them in the first place??? Our builder kit includes the following:

1 - 92mm Crankcase w/Removable Electric Starter Cover
1 - 10-Bolt Side Cover
1 - 69mm Crankshaft w/1" PTO
1 - Bare Cylinder Head
1 - MLS Headgasket
1 - Valve Cover w/Bolt
2 - Lifters
1 - Ignition Coil
1 - Fan Shroud w/Aluminum Recoil Cover
1 - Billet 32mm Intake Manifold
1 - Set of Gaskets, Seals & Bolts

Sours: http://www.prokartengineparts.com/web_pages/performance_engines_gx390.html
  1. Motorbike bicycle 16 inch
  2. E500 mercedes 2018
  3. Essential oil funnels

GX390 Race Kart


Engine & Performance

9 kW
12 hp

25 Nm
18 ft/lb

170 kg
375 lb

Power to Weight


Engine Layout










Shift Cut

Power Steering



Push to Pass


Adjustable boost

Onboard brake bias

Onboard anti-roll bar


Fuel capacity
10 L


Pre-warmed tyres

Steering Wheel
Round Small/Medium size with flat top

Tyre Compounds
Slick, Wet

Sours: https://ams2cars.info/karting/kart-race/


CarlsonMotorsports said:

That's a very open ended question.
First, you'd have to take into consideration the parts used in your build.
Stroke crank, compression piston, valve sizes, carb size, cam lift & duration, etc etc.

Running gas is not a huge deficit to alcohol (although I prefer alcohol as a race engine fuel) when it comes to making power.
That will not be your limiting factor. Detonation at higher compression ratios, less heat control, etc is more of an issue with highly modified race engines on gasoline.

Then consider that everyone's dynos will read differently....some builders offer extremely inflated numbers as part of their sales pitch or simply to dismiss the fixation racers have on "numbers."

Throwing a 50 CHP number out there may sound real impressive, but even if it's accurate...If it's in a build that's not reliable or at a usable rpm, then what's the point? My point is, it's pretty easy to build a reliable 30 CHP that's somewhat affordable. It's quite another thing to build 50 CHP. (ie it's not easy OR cheap!)

Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
Carlson Motorsports on Facebook
29 years of service to the karting industry
Linden, IN
[email protected]

Click to expand...


Not really really open ended. I said, "So what kind of HPcan a GX390make at Max 5500rpmrunning 93 Octanewith the best Parts for Endurance?"

So you have a Base GX390 a Set CC to use (88mm x 64mm) 389ccto work with. NO Big Bore or Stroker, just 389cc!

I didn't say for Racing, I said for Endurance!

I said using 93 Octane Gas, so that set's the limit on what Max CR you can use, guessing 11.5cr, probably Max CR I would want to run anyway.

You have a Set Max 5500rpmto use to pick the CAM.

So You Pick the CAM based on this Max Rpm, Valve Sizes, Carb Size, and other HD Internal/External Parts needed for Endurance!

Think of it being used at Continious 4800-5000rpmon a Mini Air Boat or Snow Glider, Hence Endurance is the key Factor. Yes, I know there are Bigger, maybe even better Engines out there, I want to keep it as light as Possible and the GX390 being the Smallest I want to use.

So Carb, CAM, Valve Sizes, CR, and HD Parts needed for Endurance, Roller Rockers, Push Rods, FlyWheel, Rod, Bolts/Studs.

I did forget to mention I want Electric Start. Will be using one of them light Weight Lithium Batterys. A 240CCA 2.4lb one turns my Yamaha Vmax 600(95hp) Snowmobile Engine better than the Old Style Lead Acid Battery ever did.


Sours: https://4cycle.com/karting/threads/gx390.90953/

Race engine gx390




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