HKM-139347
49cc Mini Sportbike — Engineered for the next generation of riders. Precision, control, and pure two-wheel excitement in a purpose-built youth platform.
Performance at a Glance
Every specification on the HKM-139347 is purposefully calibrated to deliver an accessible yet thrilling riding experience for young enthusiasts.
Engine Displacement
3.0 cu in (49cc)
2-stroke air-cooled single-cylinder powerplant
Top Speed Range
25–37 mph
40–60 km/h performance envelope
Braking System
Dual Disc
Front & rear hydraulic disc brakes
Max Load Capacity
165 lbs (75 kg)
Accommodates a broad range of young riders
Wheel Size
10 in (254mm)
Pneumatic knobby tires for versatile terrain
Transmission
Chain Drive
Reliable chain-driven power delivery
Powerplant: 49cc 2-Stroke Engine
The heart of the HKM-139347 is a compact yet energetic 49cc air-cooled 2-stroke engine. Its design philosophy centers on an exceptional power-to-weight ratio—a hallmark of 2-stroke engineering that has been refined over decades in motorsport applications worldwide.
2-Stroke Combustion Cycle
Unlike 4-stroke engines that require four piston strokes per power cycle, a 2-stroke engine completes combustion in just two strokes—compression and power—resulting in a firing event every revolution. This inherent design characteristic yields a significantly higher power density relative to displacement, which is why 49cc can propel the HKM-139347 to speeds of up to 37 mph (60 km/h). The simplified valvetrain—relying on port timing rather than poppet valves—also reduces mechanical complexity and reciprocating mass.
Air-Cooled Thermal Management
The engine employs an air-cooled architecture with strategically placed cooling fins across the cylinder head and barrel. This passive thermal management system eliminates the need for a radiator, coolant, and water pump—reducing overall weight and maintenance complexity. The fin geometry has been optimized to maximize surface area for convective heat dissipation during sustained operation.
Fuel-Oil Premix Lubrication
Consistent with 2-stroke design principles, the HKM-139347 engine uses a total-loss lubrication system where oil is premixed with fuel at a recommended ratio (typically 32:1 to 40:1 during break-in, transitioning to 40:1 to 50:1 for regular use). This method ensures every internal moving component—crankshaft bearings, connecting rod, piston rings, and cylinder walls—receives continuous lubrication during operation. Riders are advised to use high-quality 2-stroke oil meeting JASO FC or ISO-L-EGC specifications for optimal engine longevity.
Understanding 2-Stroke Power Delivery
A defining characteristic of the 2-stroke engine is its narrow but potent power band. Unlike the broad, linear torque curve of a 4-stroke, the HKM-139347's engine produces its peak output within a specific RPM range. This teaches young riders an invaluable skill: throttle modulation and gear-ratio awareness. Learning to keep the engine in its optimal rev range fosters a deeper understanding of vehicle dynamics—a foundational skill that translates directly to larger motorcycles as riders progress in their motorsport journey.
Industry data consistently shows that riders who begin on 2-stroke platforms develop more precise throttle control and a keener sense of engine feedback compared to those who start exclusively on 4-stroke machines. The HKM-139347 thus serves not merely as a recreational vehicle but as an authentic educational tool for aspiring motorcyclists.
Braking & Safety Architecture
Confidence-inspiring stopping power is fundamental to the riding experience. The HKM-139347 is equipped with a comprehensive disc braking system that delivers predictable, modulated deceleration.
Hydraulic Disc Brakes — Front & Rear
Both wheels are fitted with hydraulic disc brakes, a configuration more commonly associated with full-size motorcycles. Disc brakes offer several inherent advantages over drum alternatives: superior heat dissipation during repeated stops, more consistent performance in wet conditions, and a more linear lever feel that allows riders to modulate braking force with precision. The dual-disc layout ensures balanced deceleration, reducing the risk of front-end dive or rear-wheel lockup under hard braking.
Ergonomic Lever Design
Brake levers are sized specifically for smaller hands, with an adjustable reach mechanism that allows customization as young riders grow. The lever pivot geometry has been engineered to reduce initial bite force while maintaining progressive pressure buildup—preventing the abrupt, jerky stops that can unsettle novice riders. This thoughtful ergonomic consideration is a direct result of studying youth motor control development and grip strength data across target age demographics.
Safety Note: As with all motorized two-wheel vehicles, riders should always wear appropriate protective gear including a DOT or ECE-certified helmet, eye protection, gloves, long sleeves, full-length pants, and over-the-ankle footwear. The HKM-139347 is designed for off-road and controlled-environment use. Parental supervision is strongly recommended for all riders under the age of 16.
Chain-Driven Precision
The drivetrain is a critical interface between engine output and rear-wheel motion. On the HKM-139347, a chain-driven transmission delivers power with mechanical efficiency and durability.
Roller Chain Final Drive
The chain-driven system employs a high-tensile steel roller chain connecting the countershaft sprocket to the rear wheel sprocket. Chain drive offers superior mechanical efficiency—typically 95–98%—compared to belt or shaft drive alternatives in this displacement class. This means more of the engine's output reaches the rear wheel, contributing to the HKM-139347's responsive acceleration. Regular chain maintenance—including tension inspection, lubrication, and cleaning—will ensure consistent performance and extended service life.
Gear Ratio Optimization
The sprocket combination has been carefully selected to balance acceleration with top-end speed for the 49cc powerplant. This gearing strategy provides strong low-end responsiveness for navigating tight trails and gradual inclines, while still allowing the engine to reach its peak power RPM on open straightaways. The result is a versatile performance envelope suitable for a wide range of riding environments.
Ignition & Starting System
Dual ignition methods provide flexibility and convenience, ensuring young riders can get underway with minimal friction.
Manual & Electric Ignition Options
The HKM-139347 offers both a manual recoil starter (pull-start) and an electric ignition system. The electric start provides push-button convenience—ideal for quick restarts during riding sessions—while the manual recoil starter serves as a reliable backup and helps young riders understand the mechanical connection between their physical input and engine combustion. This dual-start architecture is a thoughtful redundancy that enhances both usability and educational value.
CDI Ignition Module
A Capacitor Discharge Ignition (CDI) system governs spark timing with electronic precision. CDI systems are prized in small-displacement engines for their rapid voltage rise time, which produces a strong, consistent spark even at high RPM. This translates to reliable cold starts, smooth idling, and crisp throttle response throughout the rev range. The sealed electronic module requires no periodic adjustment, contributing to the low-maintenance character of the ignition system.
Chassis & Rider Ergonomics
The HKM-139347's frame geometry and rider contact points have been meticulously designed around the anthropometric data of youth riders, ensuring a natural and confidence-inspiring posture.
Purpose-Built Youth Frame
The steel tubular frame is engineered with a lower center of gravity than scaled-down adult motorcycles. This deliberate design choice enhances stability at low speeds and during cornering—critical factors for riders still developing their balance and coordination skills. The seat height, handlebar reach, and footpeg placement form what ergonomists term the "rider triangle," and on the HKM-139347, this triangle has been optimized for riders within the targeted stature range. The result is a natural, relaxed riding position that reduces fatigue and allows the rider to focus on developing core motorcycling techniques such as counter-steering, body positioning, and throttle-brake coordination.
Optimized Rider Triangle
Seat height, handlebar position, and footpeg location form the three vertices of the rider triangle. On the HKM-139347, this geometry places the rider in a slightly forward-leaning sport posture that mirrors full-size sportbike ergonomics—scaled proportionally for younger riders. This position promotes active weight distribution during cornering and provides natural leverage for control inputs, all while maintaining comfort during extended riding sessions.
Suspension Compliance
The front telescopic fork and rear mono-shock suspension are tuned to absorb trail irregularities while maintaining chassis composure. Spring rates and damping characteristics have been selected for the target weight range, ensuring the suspension operates within its optimal stroke for riders between approximately 55 lbs (25 kg) and the maximum rated 165 lbs (75 kg). This compliance not only enhances comfort but also keeps the tires in consistent contact with the riding surface—a critical safety consideration.
10-Inch Wheel Platform
Wheel diameter is a foundational variable in motorcycle dynamics. The HKM-139347's 10-inch (254mm) wheels strike an optimal balance for youth riders.
Knobby Tire Pattern
The pneumatic tires feature an aggressive knobby tread pattern designed to provide traction across loose surfaces—dirt, gravel, grass, and packed earth. The tread blocks are spaced to self-clean in muddy conditions, maintaining grip when terrain becomes challenging. Tire pressure should be checked regularly; the recommended range is typically 14–18 psi (0.96–1.24 bar) for optimal balance between traction and ride comfort.
Alloy Wheel Construction
Lightweight alloy wheels reduce unsprung mass—a key metric in suspension performance. Lower unsprung weight allows the suspension to react more quickly to surface irregularities, keeping the tire in better contact with the ground. The reduced rotational inertia also contributes to quicker acceleration and more responsive braking, benefits that are particularly noticeable in a lightweight vehicle like the HKM-139347.
Technical Specifications
Comprehensive data for the HKM-139347 49cc Kids Mini Sportbike Motorcycle.
Model
HKM-139347
Engine Type
2-Stroke, Air-Cooled, Single Cylinder
Displacement
3.0 cu in (49cc)
Bore × Stroke
Approx. 1.57 × 1.57 in (40 × 40mm)
Max Power
~2.5 HP (1.9 kW) @ 6,500 RPM
Top Speed
25–37 mph (40–60 km/h)
Transmission
Chain Drive, Single-Speed
Ignition
CDI — Manual Recoil / Electric Start
Brakes
Hydraulic Disc — Front & Rear
Wheel Size
10 inches (254mm) — Alloy Rims
Max Load
165 lbs (75 kg)
Fuel Type
Gasoline + 2-Stroke Oil Premix
Cooling System
Air-Cooled (Passive Fin Design)
Frame Material
High-Tensile Steel Tubular Frame
Suspension Front
Telescopic Fork
Suspension Rear
Mono-Shock Absorber
Care & Longevity
Proper maintenance ensures years of reliable performance. The HKM-139347's mechanical simplicity makes routine care accessible.
Break-In Period Recommendations
Like all precision engines, the HKM-139347 benefits from a deliberate break-in procedure. During the first 2–3 fuel tanks, operate the engine at varying RPM levels while avoiding prolonged wide-open throttle. This allows the piston rings to properly seat against the cylinder wall, establishing an optimal sealing surface that maximizes compression and minimizes oil consumption over the engine's service life. Use a slightly richer oil mixture (32:1) during break-in before transitioning to the standard ratio.
Routine Service Intervals
Chain tension and lubrication should be inspected before every ride. The air filter element requires cleaning every 5–8 hours of operation—more frequently in dusty environments. Spark plug condition provides valuable diagnostic insight into engine health; a light tan insulator color indicates proper fuel mixture, while dark, oily deposits suggest an overly rich condition. Brake pad thickness should be visually checked monthly, with replacement recommended when friction material reaches approximately 0.08 inches (2mm).
Frequently Asked Questions
Common inquiries about the HKM-139347 49cc Kids Mini Sportbike Motorcycle.
What age range is the HKM-139347 suitable for?
The HKM-139347 is designed for youth riders typically between 6 and 14 years of age, though suitability ultimately depends on the individual rider's size, maturity, and experience level. The maximum load capacity is 165 lbs (75 kg). Riders should be able to comfortably reach the ground with both feet while seated and possess the coordination to operate throttle, brake, and steering controls simultaneously. Parental discretion and supervision are always advised.
What type of fuel and oil should I use?
Use regular unleaded gasoline with an octane rating of 87 AKI (91 RON) or higher, premixed with high-quality 2-stroke engine oil meeting JASO FC or ISO-L-EGC specifications. The recommended fuel-to-oil ratio is 40:1 (3.2 fl oz oil per 1 US gallon, or 100ml oil per 4 liters of fuel) for regular use after break-in. During the initial break-in period, a 32:1 ratio is suggested. Always mix fuel and oil thoroughly in a separate container before filling the tank.
Is assembly required upon delivery?
The HKM-139347 arrives partially assembled. Typical assembly includes installing the handlebars, front wheel, footpegs, and connecting the battery for the electric start system. Basic hand tools are required. A detailed assembly manual with step-by-step illustrations is included. Most users complete assembly within 30–60 minutes. If you are not confident in your mechanical ability, professional assembly by a qualified technician is recommended.
Can this motorcycle be used on public roads?
The HKM-139347 is designed as an off-road mini sportbike and is not street-legal in most jurisdictions. It does not come equipped with the lighting, mirrors, turn signals, or emissions certifications required for public road use. It is intended for use on private property, designated off-road trails, and closed-course environments. Always check local regulations before operating any motorized vehicle.
What safety gear is recommended?
At minimum, riders should wear a properly fitted helmet that meets DOT (FMVSS 218) or ECE 22.05/22.06 standards, eye protection (goggles or a full-face helmet with visor), full-finger gloves, a long-sleeve abrasion-resistant jersey or jacket, full-length durable pants, and over-the-ankle boots with a low heel. Additional protective equipment such as chest protectors, knee guards, and elbow guards is strongly recommended, particularly for novice riders who may experience more frequent tip-overs during the learning process.
How do I maintain the chain drive?
Chain maintenance involves three key steps: inspection, tension adjustment, and lubrication. Check chain tension before each ride—there should be approximately 0.4–0.6 inches (10–15mm) of vertical deflection at the midpoint between sprockets. Adjust via the rear axle tensioners as needed. Clean the chain periodically with a chain-specific cleaning solvent and a soft brush, then apply a quality motorcycle chain lubricant. Avoid using WD-40 or general-purpose oils, as these can fling off and provide inadequate protection under load.
Purchase with Confidence
Every HKM-139347 order is backed by comprehensive coverage designed to provide complete peace of mind.
Free Shipping on All Orders
Complimentary standard shipping on every HKM-139347 order, with no minimum purchase requirement. Tracking information is provided within 1–2 business days of dispatch, and our logistics network ensures careful handling of your motorcycle throughout transit.
180 Days Purchase Protection
A full 180-day protection window covers manufacturing defects and workmanship issues. Should any covered concern arise within six months of delivery, our support team will coordinate repair, replacement, or refund in accordance with the terms of the protection plan.
30 Days Money-Back Guarantee
If the HKM-139347 does not meet expectations for any reason, you may return it within 30 days of delivery for a full refund of the purchase price. The motorcycle must be in like-new condition with all original packaging and accessories. Return shipping coordination is provided by our customer experience team.
24 Months Warranty Service
A comprehensive 24-month warranty covers all major components including the engine, transmission, frame, suspension, and electrical system against defects in materials and workmanship. Warranty claims are processed promptly through a dedicated service portal, with replacement parts shipped at no cost for covered repairs during the warranty period.
Nationwide Service Network & Support
With over 3,000 authorized service centers across the United States, we ensure comprehensive after-sales support for your vehicle, giving you complete peace of mind.
We understand that maintenance needs may arise. When you purchase from us, you gain access to our unparalleled service ecosystem designed for maximum convenience and reliability.
1. DIY Repair & Parts Replacement:
For minor repairs or part replacements that can be handled personally, we provide cost-price genuine parts during the warranty period. Each order is accompanied by clear, step-by-step video tutorials to guide you through the self-repair process seamlessly.
2. Professional Servicing:
For issues requiring expert attention, simply contact our support team. We will locate the nearest authorized service center based on your order and location details. You only need to bring your vehicle to the designated center. Once servicing is complete, we will notify you for pickup. All repairs are free during the warranty period; afterward, only cost-based fees apply.
Rest assured—wherever you are, our extensive partner network is ready to keep your ride running smoothly.
Lifetime Limited Powertrain Warranty & Wrap Program
For added long-term security, our Lifetime Limited Powertrain Warranty and Lifetime Wrap Program provide continued mechanical breakdown coverage for as long as you own your vehicle—with no term or mileage restrictions.
Every product on Hekomart.com is expertly curated from thousands, quality tested, and lifestyle approved. Elevate your everyday.
Express Delivery Priority - Where Speed Meets Satisfaction
At Hekomart.com, we understand the anticipation that comes with every online order. While most platforms rely on standard economy shipping, we prioritize your excitement by strategically selecting premium express carriers to accelerate deliveries. Our intelligent logistics system analyzes real-time data to optimize routes, partnering with globally-recognized couriers like DHL, FedEx, and UPS to ensure 30% faster doorstep arrivals* than industry averages.
Every package receives 24/7 tracking visibility and proactive delivery updates, transforming waiting time into confidence. For time-sensitive purchases, our "Expedited Service Guarantee" offers optional priority handling at no extra cost, because your satisfaction isn't just a goal – it's the core of our delivery DNA.
*Based on internal 2025 data comparing standard shipping durations across major platforms. Delivery times vary by destination and customs procedures.
Credit Card 180 Days Purchase Protection
The 180 Days Purchase Protection protects the buyer if an item purchased has not been shipped or if a shipped item is significantly not as described by the seller. The 180 Days Purchase Protection covers all purchases and payments made through our website. We accept Visa, Master Card, American Express, and Discover Card. If you don't receive the item that you ordered, or it shows up significantly different from its description, you may qualify for Purchase Protection, and we'll reimburse you for the full purchase price plus any original shipping costs, subject to terms and limitations. If you are charged for a transaction that you didn't make, let us know within 60 days, and we've got you covered.
30 Days Money-Back Guarantee
We are confident that our products are of great quality and even better value. However, if upon receiving and inspecting your item you decide that you want to return it, you will have 30 days as of the date of shipment arrival to return it for a refund minus the shipping cost. No restocking charges. Any additional fees associated with a purchase transaction will be deducted from the amount of the refund.
24-Month Extended Warranty Service
If you purchase products from our website, you have 24 months to request repairs or replacement if any products turns out to be faulty or are not as advertised. During the warranty period if any product is found to have a manufacturer defect, we will repair or replace the defective part(s). If a product cannot be repaired or replaced within a reasonable time, you can request a refund or price reduction. We are confident that our products are of great quality and even better value. However, if upon receiving and inspecting your item you decide that you want to return it, you will have 30 days as of the date of shipment arrival to return it for a refund minus the shipping cost.
You May Also Like
HKM-975507 125cc Off-Road Dirt Bike with Disc Brakes and 61-80 km/h Speed
Regular price
$1,399.99
HKM-746131 200cc 4-Stroke Off-Road Dirt Bike for Adults with Electric Start
Regular price
$1,599.99
