Honda Engine 390cc Go Kart: How Many Horsepower Is It? Buying Guide

If you're asking how many horsepower is a 390cc Honda engine, the answer depends on the specific model and configuration. The Honda GX390, commonly used in go-karts, delivers between 11.7 HP and 13 HP at 3,600 RPM. When choosing a honda engine 390cc go kart,How many horsepower is a 390cc Honda engine?, prioritize verified net power ratings over peak claims. Look for the GX390K1 (13 HP) if maximum performance is critical, or the UT2 variant (11.7 HP) for reliable commercial-grade operation. Avoid unverified aftermarket engines lacking OEM documentation, as power output and durability may not match genuine Honda specifications.

About Honda Engine 390cc Go Kart, How Many Horsepower Is a 390cc Honda Engine?

The Honda GX390 is a 389cc (often rounded to 390cc), 4-stroke, single-cylinder, overhead valve (OHV) engine manufactured by Honda for industrial and recreational applications. Despite being marketed as a 390cc engine, its actual displacement is 389 cm³ (23.7 cu·in). It's widely used in go-karts due to its robust construction, fuel efficiency, and consistent power delivery. The question how many horsepower is a 390cc Honda engine arises frequently because advertised figures vary across retailers and engine configurations.

This engine features forced-air cooling, recoil or electric start options, and runs on unleaded gasoline with an octane rating of 86 or higher. Its horizontal shaft design makes it ideal for direct drivetrain integration in go-karts, while vertical shaft versions are typically used in pumps, generators, and pressure washers. In go-kart builds, the GX390 offers a strong balance of speed, reliability, and serviceability—making it a top choice among DIY builders and commercial track operators alike.

Why Honda Engine 390cc Go Kart, How Many Horsepower Is a 390cc Honda Engine? Is Gaining Popularity

The Honda GX390 has gained popularity in the go-karting community due to its reputation for durability, ease of maintenance, and proven performance under continuous load. Unlike small consumer-grade engines, the GX390 is built to commercial standards, meaning it can withstand hours of daily use with minimal wear when properly maintained.

One major reason for its growing adoption is consistency. Users searching for answers to how many horsepower is a 390cc Honda engine often find conflicting data online—but the GX390’s real-world performance remains stable across different setups. This predictability allows racers and rental operators to tune karts reliably and forecast performance accurately.

Additionally, parts availability and global support make repairs easier than with proprietary or lesser-known brands. Enthusiasts also appreciate that modifications such as carburetor tuning, exhaust upgrades, and clutch enhancements are well-documented within online communities, enabling incremental performance gains without sacrificing reliability.

Types and Variants

The Honda GX390 comes in several variants, each tailored for different applications. Understanding these differences is essential when evaluating a honda engine 390cc go kart,How many horsepower is a 390cc Honda engine? setup.

🛒 GX390K1 (Type S) – High-Power Horizontal Shaft

Horsepower: 13.0 HP at 3,600 RPM
Use Case: Performance go-karts, racing, high-load equipment

Pros: Highest factory-rated output, optimized for sustained performance.
Cons: Higher cost, may require upgraded cooling in enclosed kart frames.

📍 GX390 (UT2) – Standard Commercial Model

Horsepower: 11.7 HP (net rating)
Use Case: Rental fleets, utility go-karts, general-purpose machinery

Pros: Proven reliability, lower fuel consumption, widely available.
Cons: Lower peak power compared to K1; not ideal for competitive racing.

🔧 GX390 with Electric Start

Features: Includes battery-powered starting system
Use Case: Operator convenience, frequent startups, commercial operations

Pros: Easier ignition, especially in cold conditions.
Cons: Adds weight and complexity; requires battery maintenance.

🏭 Vertical Shaft Models (Non-Kart Use)

While not suitable for most go-kart designs, some sellers misrepresent vertical shaft GX390s as go-kart-ready. These are designed for pumps and compressors and lack proper mounting brackets for kart chassis.

Warning: Do not purchase vertical shaft models unless converting with a jackshaft and belt drive system.

Key Features and Specifications to Evaluate

When assessing a honda engine 390cc go kart,How many horsepower is a 390cc Honda engine?, focus on measurable technical parameters rather than marketing claims.

⚙️ Actual Displacement: 389 cm³ (not exactly 390cc)
⚡ Horsepower Rating: Confirm whether it's 11.7 HP (UT2) or 13 HP (K1); verify test standard (SAE J1349 preferred)
📌 Shaft Orientation: Must be horizontal for direct chain drive compatibility
📊 Torque Output: 26.4 Nm (19.5 lb-ft) — important for acceleration
🧰 Weight: Approximately 31.7 kg (70 lbs), affects kart balance
🌐 Fuel Requirements: Unleaded gasoline, minimum 86 octane
🔍 Cooling System: Forced-air; ensure adequate airflow in your kart frame design
📎 Mounting Pattern: Standardized, but confirm fitment with your chassis

Always request official Honda specification sheets from the seller to validate claims about how many horsepower is a 390cc Honda engine.

Pros and Cons

✅ Pros: Reliable long-term performance, excellent torque curve, widely supported globally, easy to source replacement parts, compatible with common transmissions and clutches.

❌ Cons: Heavier than smaller engines (e.g., GX270), higher initial cost than generic clones, potential for counterfeit units in third-party markets, emissions updates may slightly reduce output in newer models.

Best suited for: Adult-sized go-karts, commercial rental tracks, off-road buggies, and modified speed builds.
Not ideal for: Lightweight junior karts, budget-first projects where weight matters, or applications needing ultra-compact dimensions.

How to Choose Honda Engine 390cc Go Kart, How Many Horsepower Is a 390cc Honda Engine?

Follow this step-by-step guide to ensure you select the right GX390 model for your needs:

📋 Step 1: Define Your Use Case

Racing or recreation? → Prioritize 13 HP K1 model
Rental fleet or training? → 11.7 HP UT2 offers better longevity and fuel economy

📋 Step 2: Verify Horsepower Claims

Avoid listings claiming “up to 15 HP” — these are often exaggerated.
Look for references to SAE J1349 testing standards 1.
Cross-check model number (e.g., GX390K1 vs. UT2) with Honda’s official documentation.

📋 Step 3: Check Shaft Type and Mounting

Ensure the engine has a horizontal PTO shaft.
Confirm bolt pattern matches your kart frame or adapter plate.

📋 Step 4: Inspect for Modifications

Avoid engines with aftermarket carburetors, exhausts, or governors removed unless you’re experienced.
Modified engines may exceed safe operating limits and void warranties.

📋 Step 5: Avoid These Red Flags ❗

No serial number or illegible VIN
Sold without original packaging or manuals
Priced significantly below market average (risk of clone/fake)
Claims of “new” status but lacks Honda-branded crate or labeling

Price & Market Insights

New genuine Honda GX390 engines range from $650 to $900 USD, depending on model (K1 vs. UT2), start type (recoil vs. electric), and region. Prices may be higher in countries with import duties or limited distribution.

Used units sell between $350 and $550, depending on condition and usage history. Be cautious with used engines lacking service records.

Counterfeit or replica engines are sometimes sold as “Honda-style” or “GX390 clone” for $250–$400. While cheaper, they often deliver only 8–10 HP and have shorter lifespans due to inferior materials and tolerances.

Value Tip: For most buyers, the genuine 11.7 HP UT2 offers the best balance of price, reliability, and service life. Only upgrade to the 13 HP K1 if your application demands maximum power.

Top-Seller & Competitive Analysis

The following table compares popular GX390 variants relevant to go-kart users:

Model	Horsepower	Start Type	Typical Price (USD)	Best For
Honda GX390K1	13.0 HP	Recoil	$850	Racing, high-performance builds
Honda GX390 UT2	11.7 HP	Recoil/Electric	$700–$800	Rental fleets, general use
Clone 390cc Engine	~9.5 HP (estimated)	Recoil	$300	Budget builds (higher risk)

Note: Clone engines are not manufactured by Honda and vary significantly in quality.

Customer Feedback Synthesis

Based on aggregated user reviews and forum discussions 2, here are the most frequent points:

⭐ Positive: Longevity (many report 1,000+ hours), smooth idle, responsive throttle, easy cold starts, consistent power delivery.
🔧 Negative: Weight adds inertia to lighter karts, some newer models feel slightly detuned due to emissions controls, difficulty sourcing certain gaskets in remote areas.
❗ Complaint: Misleading horsepower claims from third-party sellers selling non-OEM engines labeled as “Honda GX390”.

Sourcing & Supplier Tips

Buy from authorized Honda Power Equipment dealers whenever possible. They provide traceable serial numbers, warranty coverage, and authentic components.

For international buyers, check Honda’s regional website to locate certified distributors. Avoid marketplace sellers offering “new” GX390s shipped from unknown warehouses without verifiable dealer credentials.

If purchasing in bulk (e.g., for a karting facility), request product conformity certificates and batch inspection reports. For resale or integration into kits, ensure compliance labeling is preserved.

Upon delivery, inspect for:

Original Honda branding and part numbers
Intact seals and packaging
Complete accessory kit (spark plug wrench, oil dipstick, bolts)

Maintenance, Safety & Legal Considerations

Regular maintenance extends engine life and maintains rated horsepower. Follow Honda’s recommended schedule:

🧼 Change oil every 25 hours or seasonally
Replace air filter and spark plug annually or per usage
Inspect fuel lines and carburetor for varnish buildup

Ensure proper guarding around the flywheel and drive system to prevent contact injuries. Use approved fuel containers and store away from living spaces.

Legally, go-karts powered by engines like the GX390 may be classified as off-road vehicles. Verify local regulations before public road use. Some jurisdictions restrict engine size, noise levels, or require safety certifications for commercial operation.

Conclusion

The Honda GX390 remains a top-tier choice for go-kart builders seeking dependable power. To answer how many horsepower is a 390cc Honda engine: expect 11.7 HP for the UT2 model and 13 HP for the GX390K1, both at 3,600 RPM. When learning how to choose honda engine 390cc go kart,How many horsepower is a 390cc Honda engine?, prioritize OEM authenticity, correct shaft orientation, and realistic power expectations.

If you need maximum speed and performance, choose the 13 HP K1 model. If you operate a rental business or value fuel efficiency and durability, the 11.7 HP UT2 is more than sufficient. Avoid clones unless budget constraints outweigh long-term reliability concerns.

FAQs

❓ How many horsepower is a 390cc Honda engine?

The Honda GX390 produces between 11.7 HP and 13 HP depending on the model. The GX390K1 delivers 13 HP, while the UT2 version outputs 11.7 HP at 3,600 RPM under SAE testing standards.

❓ Can I use a Honda GX390 on a go-kart?

Yes, provided it has a horizontal shaft. The GX390 is one of the most popular engines for adult and commercial go-karts due to its power, reliability, and widespread support.

❓ What's the difference between GX390K1 and UT2?

The GX390K1 is rated at 13 HP and designed for high-demand applications. The UT2 is a commercial model with a net rating of 11.7 HP, often used in equipment requiring consistent but moderate power.

❓ Are there fake Honda GX390 engines?

Yes. Many third-party manufacturers produce look-alike engines labeled as "Honda-style" or "compatible with GX390." These clones often underperform and lack the build quality of genuine Honda units.

❓ How fast can a go-kart with a GX390 engine go?

Depending on gearing, weight, and tire size, a go-kart with a 13 HP GX390 can reach speeds of 30–40 mph. Track conditions and driver skill also influence top speed.