Want to give your Milwaukee-Eight 114 a serious power boost? A big bore kit is a great way to do it. These kits increase your engine’s displacement, which translates to more torque and horsepower. I’ve seen some pretty impressive results from friends who’ve installed them, and it can totally transform the riding experience. But with so many options out there, choosing the right one can be tough. I’ve put together a list of some of the best big bore kits for the M8 114 to help you find the perfect upgrade.
Product Overview / Quick Summary
- S&S Cycle 128ci Big Bore Kit: Top-end performance, requires case machining.
- Fueling Parts 4.125″ Cylinder & Piston Kit: Cost-effective, reliable power upgrade.
- Cylinder Heads 4.125 Big Bore Kit: Easy installation, good for street performance.
- HPI 4.125 Big Bore Kit: High-quality components, noticeable performance gains.
- Hammer Performance 1250 Kit: Bolt-on kit, significant increase in horsepower and torque.
Top 5 Best Big Bore Kit For M8 114
1. S&S Cycle 128ci Big Bore Kit
The S&S Cycle 128ci Big Bore Kit is designed to deliver maximum performance. It turns your 114 into a powerhouse. This kit includes high-quality cylinders, pistons, and rings engineered for serious power gains.
Pros:
- ✅ Provides a significant increase in horsepower and torque.
- ✅ High-quality components ensure durability and reliability.
- ✅ S&S Cycle is a trusted name in performance upgrades.
Cons:
- ❌ Requires case machining, which adds to the installation cost and complexity.
- ❌ Higher price point compared to other kits.
- ❌ May require additional upgrades to support the increased power, like a stronger clutch.
Verdict: If you’re looking for maximum performance and don’t mind the extra cost and effort of case machining, the S&S Cycle 128ci Big Bore Kit is a top choice.
2. Fueling Parts 4.125″ Cylinder & Piston Kit
The Fueling Parts 4.125″ Cylinder & Piston Kit is a great option for those seeking a reliable and cost-effective power upgrade. This kit is designed to improve the overall performance of your M8 114 without breaking the bank.
Pros:
- ✅ Offers a noticeable improvement in horsepower and torque.
- ✅ More affordable than some of the high-end kits.
- ✅ Good quality components for the price.
Cons:
- ❌ May not provide the same level of performance as higher-end kits.
- ❌ Limited information available on long-term reliability compared to more established brands.
- ❌ Installation can be tricky; professional installation recommended.
Verdict: This kit is a solid choice for riders looking for a budget-friendly way to boost their M8 114’s performance without sacrificing reliability.
3. Cylinder Heads 4.125 Big Bore Kit
This kit is designed for easy installation and improved street performance. It provides a good balance of power and ease of use, making it a popular choice for riders who want a hassle-free upgrade.
Pros:
- ✅ Relatively easy installation compared to other kits.
- ✅ Provides a noticeable increase in power and torque.
- ✅ Good for everyday street riding and touring.
Cons:
- ❌ May not be the best choice for high-performance applications.
- ❌ The quality of components may not be as high as some of the more expensive kits.
- ❌ Limited customization options.
Verdict: If you’re looking for a straightforward upgrade that will improve your M8 114’s performance without requiring extensive modifications, this kit is a good option.
4. HPI 4.125 Big Bore Kit
The HPI 4.125 Big Bore Kit is known for its high-quality components and noticeable performance gains. HPI is a reputable brand in the motorcycle performance industry, and this kit reflects their commitment to quality.
Pros:
- ✅ High-quality cylinders, pistons, and rings.
- ✅ Delivers a significant increase in horsepower and torque.
- ✅ Improved throttle response and overall performance.
Cons:
- ❌ Higher price point compared to some other kits.
- ❌ Installation may require some technical expertise.
- ❌ Availability may be limited depending on your location.
Verdict: This kit is a great choice for riders who are willing to invest in high-quality components and want a noticeable improvement in their M8 114’s performance.
5. Hammer Performance 1250 Kit
The Hammer Performance 1250 Kit is a bolt-on kit designed to provide a significant increase in horsepower and torque. This kit is popular among riders who want a simple and effective way to upgrade their M8 114’s performance.
Pros:
- ✅ Bolt-on installation, no case machining required.
- ✅ Significant increase in horsepower and torque.
- ✅ Comprehensive kit includes everything you need for the upgrade.
Cons:
- ❌ May require additional tuning to optimize performance.
- ❌ Can be expensive compared to other kits.
- ❌ Not emissions compliant in all areas.
Verdict: If you’re looking for a powerful and relatively easy-to-install upgrade for your M8 114, the Hammer Performance 1250 Kit is an excellent choice.
Buying Guide
Choosing the right big bore kit for your M8 114 can feel overwhelming, but focusing on a few key factors will help you narrow down your options. Here’s what to consider:
- Performance Goals: What are you hoping to achieve? Are you looking for maximum horsepower for racing, or a more modest boost for everyday riding? Different kits offer different levels of performance.
- Budget: Big bore kits vary significantly in price. Set a budget beforehand to avoid overspending. Remember to factor in installation costs, as some kits require professional installation.
- Installation Complexity: Some kits are bolt-on, meaning they can be installed without any major modifications. Others require case machining or other specialized work. Consider your mechanical skills and whether you’re comfortable tackling a more complex installation. If not, factor in the cost of professional installation.
- Component Quality: Look for kits that use high-quality components from reputable manufacturers. This will ensure durability and reliability. Read reviews and do your research to find kits that are known for their quality.
- Compatibility: Make sure the kit is specifically designed for your M8 114 engine. Check the manufacturer’s specifications to ensure compatibility. Also, consider any other modifications you’ve made to your bike, such as exhaust or air intake, and whether the kit is compatible with those modifications.
- Tuning: After installing a big bore kit, you’ll likely need to tune your engine to optimize performance. Some kits come with pre-programmed tunes, while others require custom tuning. Factor in the cost of tuning when choosing a kit.
FAQs
Q: Will a big bore kit void my warranty?
A: Yes, installing a big bore kit will likely void your factory warranty, as it’s a significant modification to your engine. Check with your dealer or warranty provider for specific details.
Q: Do I need to upgrade my exhaust or air intake when installing a big bore kit?
A: It’s highly recommended. A big bore kit increases the amount of air and fuel your engine needs. Upgrading your exhaust and air intake will help your engine breathe better and maximize the performance gains from the kit.
Q: Can I install a big bore kit myself?
A: It depends on your mechanical skills and the complexity of the kit. Some kits are easier to install than others. If you’re not comfortable working on your engine, it’s best to have a professional install the kit.
Q: How much horsepower can I expect to gain from a big bore kit?
A: Horsepower gains vary depending on the kit and the specific setup of your engine. However, you can typically expect to see a significant increase in horsepower and torque, often in the range of 20-40 horsepower.
Conclusion
Upgrading your M8 114 with a big bore kit can be an awesome way to unlock its full potential. Whether you prioritize maximum power, ease of installation, or budget-friendliness, there’s a kit out there for you. Remember to consider your performance goals, budget, and mechanical skills when making your decision. Do your research, read reviews, and choose a kit that’s right for you. With the right kit and a proper installation, you’ll be enjoying a whole new level of performance from your Harley-Davidson.
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