We researched and compared the top big bore kits available for 50cc scooters, analyzing manufacturer specifications, owner feedback, and industry standards. Our evaluation focuses on performance gains, build quality, ease of installation, and safety considerations to help you choose the right upgrade for your scooter.
| Photo | Product | Score | Buy |
|---|---|---|---|
|
🚗
|
Naraku 72cc Big Bore Kit Best Overall 72cc displacement, cast iron cylinder, includes piston rings and gaskets |
9.0 | 🛒 Check Price |
|
🚗
|
Polini 70cc Big Bore Kit Best for High RPM 70cc displacement, aluminum-cylinder with nikasil coating, forged piston |
8.7 | 🛒 Check Price |
|
🚗
|
Mallossi 70cc Big Bore Kit Best Value 70cc displacement, cast iron cylinder, includes piston, rings, and gaskets |
8.4 | 🛒 Check Price |
|
🚗
|
Stage6 80cc Big Bore Kit Maximum Displacement 80cc displacement, aluminum cylinder with nikasil coating, includes piston and rings |
8.1 | 🛒 Check Price |
|
🚗
|
Airsal 70cc Big Bore Kit Best for Daily Riding 70cc displacement, cast iron cylinder, includes piston, rings, and gaskets |
8.3 | 🛒 Check Price |
|
🚗
|
Top Performance 70cc Big Bore Kit Best for Beginners 70cc displacement, cast iron cylinder, includes piston, rings, and gaskets |
7.8 | 🛒 Check Price |
|
🚗
|
Metrakit 70cc Big Bore Kit Budget Pick 70cc displacement, cast iron cylinder, includes piston and rings |
7.3 | 🛒 Check Price |
1. Naraku 72cc Big Bore Kit: Best Overall
The Naraku 72cc Big Bore Kit stands out as our top pick due to its balance of performance and reliability. In our evaluation, the cast iron cylinder offers superior heat management compared to aluminum alternatives, which enhances longevity. Owner feedback consistently reports a noticeable increase in acceleration and top speed without compromising daily drivability. The kit includes all necessary components, making installation straightforward for those with basic mechanical skills.
However, this kit is not a simple bolt-on; it typically requires carburetor rejetting and possibly an upgraded exhaust to fully realize its potential. Riders seeking a plug-and-play solution may find the tuning demands challenging. We recommend this kit for owners willing to invest time in fine-tuning for maximum gains.
- Significant power increase from 50cc to 72cc for improved acceleration and top speed
- Cast iron cylinder provides excellent heat dissipation and long-term durability
- Includes all necessary gaskets and piston rings for a complete installation
Pros: Noticeable performance gain; Durable construction; Complete kit with quality components
Cons: May require carburetor rejetting for optimal performance
2. Polini 70cc Big Bore Kit: Best for High RPM
The Polini 70cc Big Bore Kit is engineered for riders who prioritize top-end power and high-RPM performance. Our research indicates that the nikasil coating on the aluminum cylinder provides low friction, allowing the engine to rev freely. The forged piston is both lighter and stronger than cast alternatives, contributing to reduced reciprocating mass. Owner feedback from sport scooter enthusiasts highlights significant gains in peak horsepower, particularly with supporting modifications like a performance exhaust and larger carburetor.
On the downside, the aluminum cylinder may not be as durable as cast iron under sustained high loads, and the kit demands meticulous maintenance. It is less forgiving of lean fuel mixtures or poor oil quality. We recommend this kit for experienced tuners who are comfortable with regular engine checks and adjustments.
- Nikasil-coated aluminum cylinder reduces friction and improves high-RPM performance
- Forged piston offers higher strength and lighter weight for rev-happy engines
- Designed for aggressive riding and racing applications
Pros: Excellent high-RPM power; Lightweight components reduce engine stress; Proven in racing environments
Cons: Higher cost than cast iron options; May wear faster if not properly maintained
3. Mallossi 70cc Big Bore Kit: Best Value
The Mallossi 70cc Big Bore Kit offers a compelling balance of cost and performance, making it our value pick. In our evaluation, the cast iron cylinder provides durable and predictable power, especially in the low-to-mid RPM range where most daily riding occurs. Owner feedback praises the kit for its straightforward installation, often requiring only basic tools and no major modifications. The included gaskets and piston rings are of good quality, reducing the risk of leaks.
However, this kit does not deliver the same peak horsepower as more expensive options, and its heavier construction can slightly reduce engine responsiveness. It is best suited for commuters or casual riders seeking a reliable power increase without breaking the bank. Those chasing maximum performance should consider higher-end kits.
- Affordable upgrade with reliable performance gains
- Cast iron cylinder construction for consistent power delivery
- Comprehensive kit with all necessary hardware
Pros: Budget-friendly without sacrificing quality; Easy installation process; Good low-to-mid range torque
Cons: Limited top-end power compared to premium kits; Heavier than aluminum alternatives
4. Stage6 80cc Big Bore Kit: Maximum Displacement
The Stage6 80cc Big Bore Kit pushes the boundaries of what a 50cc scooter engine can handle. Our research shows that this kit offers the largest displacement increase, translating to substantial horsepower gains when paired with a performance exhaust, larger carburetor, and upgraded clutch. The nikasil-coated aluminum cylinder keeps weight low, aiding in engine response. Owner feedback from the racing community highlights impressive dyno numbers.
However, this kit is not for the faint of heart. Installation requires significant engine case machining, and the increased stress on the crankshaft and bearings can lead to premature failure. It is best suited for experienced builders who accept the trade-offs for maximum performance. Daily riders should avoid this kit due to its demanding maintenance and reduced reliability.
- Largest displacement in our lineup for maximum power potential
- Lightweight aluminum construction reduces engine load
- Designed for experienced tuners seeking extreme performance
Pros: Highest power output; Lightweight cylinder; Suitable for racing setups
Cons: Requires extensive engine modifications; Reduced reliability and engine life
5. Airsal 70cc Big Bore Kit: Best for Daily Riding
The Airsal 70cc Big Bore Kit is tailored for riders who prioritize reliability and ease of use over raw power. In our evaluation, the cast iron cylinder offers excellent durability and consistent performance over time. Owner feedback indicates that the kit installs with relative ease, often without the need for carburetor rejetting if the stock carburetor is in good condition. The power increase is noticeable but not overwhelming, making it ideal for daily commuting.
That said, this kit may disappoint those seeking dramatic acceleration gains. Its heavier construction can slightly affect handling, though most riders will not notice. We recommend it for scooter owners who want a dependable upgrade that will not require constant tinkering.
- Reliable cast iron construction for long-term daily use
- Smooth power delivery suitable for commuting
- Easy installation with minimal modifications required
Pros: Dependable performance; Low maintenance needs; Good value for daily riders
Cons: Modest power gain; Heavier than aluminum kits
6. Top Performance 70cc Big Bore Kit: Best for Beginners
The Top Performance 70cc Big Bore Kit is designed with novice mechanics in mind. Our research indicates that the installation process is straightforward, and the included instructions are clear. Owner feedback from first-time upgraders praises the kit for its simplicity and the noticeable but manageable power increase. The cast iron cylinder provides reliable performance, though it does not match the output of higher-end kits.
However, experienced riders may find the power gains underwhelming, and the overall build quality is not as robust as some alternatives. The kit is best suited for those new to scooter modification who want a safe, low-risk upgrade. Enthusiasts looking for serious performance should look elsewhere.
- User-friendly installation with clear instructions
- Moderate power increase suitable for first-time tuners
- Cast iron cylinder for consistent performance
Pros: Beginner-friendly; Affordable price point; Good support from manufacturer
Cons: Lower power output than competitors; Materials feel less premium
7. Metrakit 70cc Big Bore Kit: Budget Pick
The Metrakit 70cc Big Bore Kit is the most economical choice for those on a tight budget. Our research shows that it provides a modest power increase, but owner feedback is mixed regarding fit and finish. Some users report that the piston rings and gaskets are of lower quality, leading to potential oil leaks or compression loss. The cast iron cylinder is adequate for basic use, but the kit does not include detailed installation instructions.
We recommend this kit only for budget-conscious buyers who are comfortable with potential troubleshooting. It is not suitable for riders seeking reliability or significant performance gains. Those willing to spend a bit more will likely get a better overall experience with other options.
- Lowest cost option in our lineup
- Basic power increase for budget-conscious riders
- Cast iron cylinder for decent durability
Pros: Very affordable; Simple design
Cons: Inconsistent quality control; Limited performance gain; May require additional tuning
Frequently Asked Questions
What is a big bore kit and how does it work?
A big bore kit replaces the stock cylinder and piston with a larger diameter set, increasing engine displacement. This allows more air and fuel into the combustion chamber, resulting in more power and torque. Most kits include a cylinder, piston, rings, and gaskets.
Will a big bore kit damage my scooter engine?
When installed correctly and with proper tuning, a big bore kit can be reliable. However, it increases stress on the crankshaft, bearings, and transmission. Using high-quality oil, upgrading the carburetor and exhaust, and ensuring proper jetting can mitigate risks. Kits with large displacement increases may shorten engine life.
Do I need to upgrade other parts when installing a big bore kit?
Often yes. A larger carburetor, performance exhaust, and stronger clutch are recommended to fully utilize the kit’s potential. At minimum, rejetting the carburetor is usually required to avoid a lean condition that can cause overheating and engine damage.
Can I install a big bore kit myself?
If you have basic mechanical skills and tools, many kits can be installed at home. The process involves removing the cylinder head, swapping the cylinder and piston, and reassembling. However, for larger kits requiring case machining, professional installation is recommended.
What is the best big bore kit for a 50cc scooter?
The best kit depends on your goals. For overall performance and reliability, the Naraku 72cc kit is our top pick. For high-RPM power, the Polini 70cc kit excels. For value, the Mallossi 70cc kit offers good performance at a lower cost. Consider your skill level and desired power increase.
Our Verdict
After researching and comparing these big bore kits, we recommend the Naraku 72cc Big Bore Kit as the top pick for its excellent balance of power, durability, and value. The Polini 70cc Big Bore Kit is a strong runner-up for riders focused on high-RPM performance. Choose based on your specific needs and willingness to perform additional tuning.
