Looking to boost your 50cc scooter’s performance? A big bore kit is one of the most effective ways to dramatically increase power, acceleration, and top speed. These kits essentially increase the displacement of your engine, giving it more “oomph.” We’ve scoured the market to find the best big bore kits for 50cc scooters that offer reliability, performance, and great value. Whether you’re a seasoned mechanic or a DIY enthusiast, upgrading your scooter has never been easier or more rewarding.
Quick Product Comparison
Our Top 4 Best Big Bore Kit For 50Cc Scooter Reviews – Expert Tested & Recommended
1. Kymlaa GY6 100cc Big Bore Cylinder Rebuild Kit
The Kymlaa GY6 100cc big bore cylinder rebuild kit is designed for 49cc/50cc 139QMB engines, offering a significant performance boost. This kit effectively upgrades your GY6 50cc, 60cc, or 80cc engine to a powerful 100cc without needing an EGR system, leading to higher RPMs and faster maximum speeds. The 69mm valve length version ensures great durability and reliability for daily use.
Key Features That Stand Out
- ✓ Increases engine displacement to 100cc
- ✓ Compatible with 49cc/50cc 139QMB engines
- ✓ Features a 69mm valve length for optimized performance
- ✓ Enhances RPM, power, and maximum speed
Why We Recommend It
This kit is an excellent choice for riders seeking a noticeable increase in power and speed. It’s well-regarded for its straightforward installation and the immediate performance gains it provides, making your scooter feel like a completely different machine.
Best For
Ideal for scooter owners looking to upgrade their 50cc engine for improved performance in daily commuting and recreational riding.
Pros and Cons
Pros:
- Significant power and speed increase
- Good quality components for the price
- Relatively easy installation for experienced DIYers
- Enhances acceleration and hill-climbing ability
Cons:
- Spark plug and CDI may require replacement with higher-quality parts
- No detailed instructions included
Customer Reviews
Customer Review: If there is a single bad review on this item it was either a fluke or lack of installer experience. This kit came exactly as shown. Was very easy to install, and took 2 hours total and wasn’t even rushing. Watch a few YouTube videos and DO NOT RUSH! Everything went together perfect, and smooth. All parts including exhaust studs were absolutely fine and same as stock. Bike started up within a few cranks once gas got back in to the carb. The power is night and day. Have no problem getting my tao 50 pony up to 40-45mph now, and quickly. Pulls wheelies fairly easily now as well. Literally was getting smoked by my buddies mopeds earlier in the day, and went back to his house after install and put bus lengths on his 2 stroke moped. Much more responsive. Keep in mind I already had an upgraded jet (85) and intake and exhaust and a 7/5gram split slider swap. But literally runs perfect as is with only a small idle adjustment. Highly suggest this kit. I haven’t even installed the cdi, clutch springs, or big main engine gaskets either. Only complaint I have is the spark plugs that keep coming with these kits and the cdi kits are trash. Use ur stock plug or a new stock one. Other then that we’ll worth the money and definitely a good buy.
Customer Review: kit really worked well. ridden over 300 miles in one weekend at full speed!
2. Trkimal GY6 100cc Big Bore Cylinder Rebuild Kit
The Trkimal GY6 100cc big bore kit is designed to enhance the performance of your 49cc/50cc 139QMB moped scooter. This kit provides a substantial increase in engine displacement, boosting RPMs and overall power for a faster, more thrilling ride. Its 64mm valve length ensures it’s well-suited for everyday use while maintaining excellent durability.
Key Features That Stand Out
- ✓ Transforms 50cc engines to 100cc
- ✓ Improves acceleration and top speed
- ✓ Features a 64mm valve length
- ✓ Designed for durability and reliability
Why We Recommend It
This kit is a solid choice for scooter owners who want a noticeable performance upgrade. It delivers a significant power surge, making your scooter feel much more capable and enjoyable to ride, especially when paired with other minor upgrades.
Best For
Perfect for riders wanting a noticeable power upgrade on their 50cc GY6 scooter without overhauling the entire engine.
Pros and Cons
Pros:
- Greatly enhances engine power and torque
- Noticeable difference in acceleration and speed
- High-quality construction
- Improves the overall riding experience
Cons:
- Gaskets can be creased during shipping due to inadequate packaging
- Potential for manufacturing defects in specific components (e.g., valve seat)
Customer Reviews
Customer Review: This is the best performance upgrade you can do to any 50cc. Make sure you tune the carb after install. I found it easier to install the piston first and letting it stick slightly out the bottom before sleeving the cylinder wall down.before this kit the motor is a pipsqueak and power weak, after the install, it has torque. Dang what a difference. The scoot has some actual pull to it now. The first thing I noticed starting itwith the bigger piston is the growl it makes- Has a louder Deeper thump of a sound makes it very nice. And riding it – waay more power. Everything looks well made and durable. Also this kit pairs great with the gear up kit for more top speed
Customer Review: DISAPPOINTED!!!Dingbats at Amazon FOLDED THE GASKETS!! I was able to make them work, though. While trying to save pennies on a larger box, they forced it into the smallest box possible and creased some of the gaskets. DUHHHH!!!The exhaust valve seat/ exhaust valve and spring assembly was incorrectly machined, causing a combustion leak.I didn’t check beforehand because I’ve had great luck with this same kit in the past.No matter what I did, the engine wouldn’t idle correctly and was extremely hard to start. Initially, I thought it was a carb tuning issue, but after multiple jetting and needle changes, the problem persisted.I eventually pulled the head off and checked it closely. It looks like the exhaust valve seat area was incorrectly machined. The valve spring sits too far inside the head and the spring has very little tension.Otherwise, everything was great quality and went together without a hitch.I was very surprised because the kit I installed on my previous bike worked beautifully for several thousand miles.I will attempt to make a return and see what happens with the new one.I AM NOT HAPPY that I have to do this TWICE!!! I’m ready to RIDE!! 👍💥EDIT💥Amazon shipped a new kit. Gaskets were packed the same way but not creased this time. The (2nd) new kit worked perfectly. Same as the first one I bought a couple of years ago. 👍Adding a star!
3. Glixal GY6 100cc 50mm Big Bore Cylinder Rebuild Kit
The Glixal GY6 100cc 50mm big bore cylinder rebuild kit comes with a performance head, ideal for upgrading your 139QMB scooter or moped engine. This kit features larger valves (18.5/20.5mm) compared to stock (16/18.5mm) to allow for more power. It’s compatible with 69mm long valve heads, and if your original head has 64mm valves, you’ll need to swap the rocker arms included in this kit. This is a fantastic option for those on a budget looking for a significant power boost.
Key Features That Stand Out
- ✓ Includes a performance cylinder head with larger valves
- ✓ Upgrades engine to approximately 82cc (feels like 100cc)
- ✓ Comes with replacement rocker arms if needed
- ✓ Excellent value for money
Why We Recommend It
This Glixal kit offers a compelling performance upgrade at an attractive price point. It’s a great way to add significant power and speed to your scooter, making it more enjoyable for commuting and general riding, even on hills.
Best For
Budget-conscious riders looking for a substantial performance upgrade for their 50cc GY6 scooter.
Pros and Cons
Pros:
- Impressive power gains for the price
- Includes essential components like a performance head and rocker arms
- Easily boosts scooter’s top speed and acceleration
- Good for everyday use after proper tuning
Cons:
- Valve springs may not be the highest quality
- Included CDI box is often considered low quality
- Exhaust studs can be weak
Customer Reviews
Customer Review: I’m editing my review, since I just had to teardown my engine today. The exhaust valve spring broke. So I am gonna replace the springs this weekend. Luckily nothing else was damaged. Other than that the kit has been good. The cdi box was junk (good luck finding a decent cdi box for a 50cc) and the exhaust studs are junk. So if I was doing this again, I would get better studs for the exhaust and try to get higher quality valve springs.This kit is such a great deal. Before this kit my scooter had a top speed of 38mph and going up hills it would drop down to 10mph sometimes. I put this kit on and the acceleration is awesome. I have no problem keeping up with with traffic now and even steep hills I can cruise over 30mph. I’m waiting to break in the motor before I really find my top speed, but I’ve had it up to 45mph, GPS verified so far. The new ignition system, variator weights, and clutch springs are a great bonus. Installation is easy enough.I left the engine on the bike. You’ll need a socket set with 8-10mm shallow and deep sockets, feeler gauges, torque wrench something to clean any old gasket material and screwdrivers and wrenches. A hobby mechanic should be able to complete this install in under 5 hours. Other upgrades I have done so far are a new carb with 85 main jet, free flowing air filter new variator and weights and black performance exhaust. I got a new 2000rpm clutch but I haven’t installed it yet. All ordered off Amazon!A final note. This kit will make your 49-50cc sooter 82cc not 100cc. But those 32cc will feel like 100 for sure.
Customer Review: Awesome. Ive been using this kit for over a month now and its powerful. That being said i keep my rpms below 8k just because I dont trust the valve springs. I’ll be upgrading the springs to better ones just in case. Ive bought 2 of these so far and am likely to get another for my spare scooter
4. GY6 47mm Big Bore Kit
This GY6 47mm big bore kit is designed to upgrade your 50cc 139QMB moped scooter engine to 80cc. It includes all the necessary components for a successful upgrade, such as the cylinder block, piston, ring set, pin, clips, and gaskets. This kit is an excellent entry-level option for those looking to experience the benefits of increased displacement and power without a significant investment.
Key Features That Stand Out
- ✓ Increases engine displacement from 50cc to approximately 80cc
- ✓ Comprehensive kit includes cylinder, piston, rings, and gaskets
- ✓ Easy installation for noticeable power gains
- ✓ Great value for an engine upgrade
Why We Recommend It
This kit offers a straightforward and affordable way to boost your scooter’s performance. It provides a tangible increase in power and is a great starting point for anyone new to engine modifications. While it might not offer the extreme performance of larger kits, it delivers a solid improvement for everyday riding.
Best For
Beginners or riders looking for a simple and cost-effective way to increase their 50cc scooter’s engine size and power.
Pros and Cons
Pros:
- Great value for the price
- Noticeable increase in power and acceleration
- Includes all necessary parts for the upgrade
- Easy to install for those with basic mechanical skills
Cons:
- May require a compatible head with larger valves for optimal performance
- No specific instructions provided
Customer Reviews
Customer Review: Works as it should. Great value for the money. Fit nicely and was easy to install.
Customer Review: good product, I had compression troubles so i had to buy a head with bigger valves because the pressure was too much for the small valves in the old headhas no instructions at all but you can google how to install it in about two hours and you will notice a increase in power right away
Complete Buying Guide for Best Big Bore Kit For 50Cc Scooter
Essential Factors We Consider
When selecting the best big bore kit for a 50cc scooter, we look at several critical factors. First and foremost is the quality of materials and manufacturing. A well-made kit ensures longevity and prevents potential engine damage. We also consider the increase in displacement – how much bigger does the kit make your engine? This directly correlates to the performance gains you can expect. Compatibility is also key; we prioritize kits designed for the common GY6 139QMB engines found in most 50cc scooters. Finally, ease of installation and the inclusion of all necessary components are vital for a smooth upgrade process. If you’re looking into other performance upgrades, checking out a bike tool kit for beginners might be a good starting point for general maintenance.
Budget Planning
Big bore kits for 50cc scooters can range in price, but generally, you can find excellent options without breaking the bank. For a basic upgrade to around 80cc, expect to spend anywhere from $50 to $100. More comprehensive kits, offering larger displacements (like 100cc) and higher-quality components, might cost between $100 and $200. It’s important to factor in potential additional costs, such as a larger carburetor, upgraded exhaust, or performance clutch, which can sometimes enhance the benefits of a big bore kit. Investing in a good pump for racing bikes (or scooters!) can also ensure your tires are properly inflated for optimal performance after an upgrade.
Final Thoughts
Upgrading your 50cc scooter with a big bore kit is a fantastic way to inject new life and power into your ride. Whether you’re looking for a slight performance bump or a significant increase in speed and acceleration, there’s a kit out there for you. Remember to consider your budget, mechanical skill level, and desired performance outcome when making your choice. Always ensure you follow installation instructions carefully, and consider consulting with a professional if you’re unsure about any step. Proper tuning after installation is crucial for optimal performance and engine longevity.
Frequently Asked Questions
Q: What is a big bore kit for a 50cc scooter?
A: A big bore kit increases the diameter of your scooter’s cylinder, thereby increasing the engine’s displacement (e.g., from 50cc to 80cc or 100cc). This allows the engine to burn more fuel and air, resulting in more power, torque, and higher top speeds.
Q: Will a big bore kit make my scooter street legal?
A: This depends on local regulations. In many places, modifying an engine to exceed its original displacement may render it illegal for street use without proper certification or registration. Always check your local laws and regulations before installing a big bore kit.
Q: What other upgrades do I need when installing a big bore kit?
A: While not always strictly necessary, it’s highly recommended to upgrade your carburetor with a larger one, and potentially your exhaust system, to match the increased airflow and fuel demands of the bigger engine. A performance air filter can also be beneficial.
Q: How difficult is it to install a big bore kit?
A: Installation requires a good understanding of small engine mechanics. It involves disassembling the top end of the engine. If you’re not comfortable with engine work, it’s best to have a professional mechanic install it. Having a comprehensive tool kit is essential for any DIY installation.
Q: How much faster will my scooter be after installing a big bore kit?
A: The increase in speed and power varies depending on the specific kit, other modifications, and the scooter’s original condition. However, you can typically expect a noticeable improvement, often adding 5-15 mph to your top speed and significantly improving acceleration.
Choosing the right big bore kit for your 50cc scooter can transform your riding experience, giving you the power and performance you’ve been craving. We hope this guide helps you make an informed decision. If you’re ready to take your scooter’s performance to the next level, now is the perfect time to upgrade!
