Thinking about unleashing some extra power from your Polaris Rzr 170 with a big bore kit? It’s a tempting upgrade, promising more pep for those off-road adventures. While a big bore kit can definitely breathe new life into your Rzr 170, it's not always a straightforward bolt-on solution. Understanding the potential pitfalls beforehand can save you a lot of headache, time, and money.

The Allure of More Power: Why a Big Bore Kit?

The Polaris Rzr 170 is a fantastic entry-level UTV, perfect for younger riders or those looking for a nimble machine. However, its stock 169cc engine can sometimes feel a little…underwhelming, especially when tackling hills or carrying a passenger. A big bore kit increases the engine's displacement, typically to around 190cc or even 200cc, resulting in a noticeable boost in horsepower and torque. This translates to improved acceleration, better hill-climbing ability, and a more responsive overall driving experience. The promise of more power is what drives many Rzr 170 owners to consider this upgrade.

Not All Sunshine and Rainbows: Potential Problems to Watch Out For

While the idea of increased power is appealing, installing a big bore kit isn’t always a seamless process. Various issues can arise, ranging from installation challenges to long-term reliability concerns. Let's delve into some of the most common problems you might encounter.

1. Installation Headaches: It's Not Always "Plug and Play"

  • Incorrect Installation: This is probably the biggest culprit behind many big bore kit problems. Proper installation is absolutely crucial. Failing to follow the instructions meticulously, using incorrect tools, or lacking the necessary mechanical expertise can lead to a host of issues, including poor performance, engine damage, and even complete engine failure. Always double-check clearances, torque specs, and ensure proper gasket sealing.
  • Cylinder Head Mismatch: Some big bore kits require modification to the cylinder head for optimal performance. This could involve porting, polishing, or even replacing the valves. If the cylinder head isn't properly matched to the new cylinder and piston, you might not see the expected power gains and could even experience engine damage.
  • Timing Issues: Installing a big bore kit can sometimes affect engine timing. If the timing is off, the engine won't run efficiently, and you could experience poor performance, misfires, and even engine damage. Always verify and adjust the timing after installing a big bore kit.
  • Fuel Delivery Problems: A larger cylinder requires more fuel. The stock carburetor or fuel injection system might not be able to provide enough fuel to meet the increased demand, leading to a lean running condition. A lean condition can cause overheating, detonation (knocking), and ultimately, engine damage.

2. Reliability and Durability Concerns: Can Your Rzr Handle the Extra Oomph?

  • Increased Stress on Engine Components: A big bore kit increases the stress on various engine components, including the crankshaft, connecting rod, and bearings. These components might not be designed to handle the increased power output, leading to premature wear and failure.
  • Overheating: The larger cylinder generates more heat. If the cooling system isn't upgraded to handle the increased heat load, the engine can overheat, leading to damage to the cylinder head, piston, and other components.
  • Piston Ring Issues: The piston rings are responsible for sealing the combustion chamber and preventing oil from entering. If the piston rings aren't properly installed or are of poor quality, they can fail prematurely, leading to oil consumption, reduced compression, and poor performance.
  • Cylinder Wear: A poorly installed or low-quality big bore kit can lead to increased cylinder wear. This can result in reduced compression, poor performance, and eventually, the need for a complete engine rebuild.

3. Tuning and Carburetion Challenges: Getting the Air/Fuel Mixture Just Right

  • Lean Running Conditions: As mentioned earlier, a big bore kit often requires adjustments to the fuel system. If the engine is running lean (too much air, not enough fuel), it can overheat and suffer from detonation.
  • Rich Running Conditions: Conversely, if the engine is running rich (too much fuel, not enough air), it can lead to poor fuel economy, fouled spark plugs, and reduced performance.
  • Difficulty in Tuning: Achieving the optimal air/fuel mixture can be challenging, especially with a carburetor. It often requires experimenting with different jet sizes and needle settings. Fuel injection systems may require a programmer or tuner to properly adjust the fuel maps.
  • Altitude Adjustments: The air/fuel mixture needs to be adjusted based on altitude. What works well at sea level might not work well at higher elevations.

4. Part Compatibility Issues: Making Sure Everything Plays Nice Together

  • Exhaust System Restrictions: The stock exhaust system might be too restrictive for the increased airflow of a big bore kit. This can limit performance and even cause backpressure issues.
  • Air Filter Limitations: A restrictive air filter can also limit performance. Upgrading to a high-flow air filter is often necessary to take full advantage of the big bore kit.
  • Clutch Performance: With the increased power, the stock clutch might not be able to effectively transfer the power to the wheels. This can lead to clutch slippage and reduced acceleration.
  • Electrical System Strain: The increased power output can put a strain on the electrical system, particularly the charging system.

Avoiding the Pitfalls: Tips for a Successful Big Bore Kit Installation

So, how do you ensure a successful big bore kit installation and avoid these potential problems? Here are some crucial tips:

  • Choose a Reputable Kit: Do your research and select a big bore kit from a reputable manufacturer known for quality and reliability. Read reviews and ask for recommendations from other Rzr 170 owners.
  • Thoroughly Read the Instructions: This seems obvious, but it's often overlooked. Read the installation instructions carefully and understand each step before you begin.
  • Use Proper Tools: Using the correct tools is essential for a successful installation. Don't try to cut corners by using makeshift tools.
  • Ensure Proper Gasket Sealing: Use new gaskets and apply sealant where necessary to ensure a proper seal. Leaks can lead to loss of compression and other problems.
  • Verify Clearances: Check all clearances, such as piston-to-valve clearance and piston-to-cylinder wall clearance, to ensure that everything is within specifications.
  • Torque to Specification: Use a torque wrench to tighten all bolts to the specified torque values. Over-tightening or under-tightening can lead to problems.
  • Upgrade Fuel Delivery: Consider upgrading the carburetor or fuel injection system to ensure that the engine is receiving enough fuel. This might involve installing larger jets, a new fuel pump, or a fuel controller.
  • Upgrade Cooling System: If you anticipate riding in hot conditions or pushing the engine hard, consider upgrading the cooling system with a larger radiator or an oil cooler.
  • Upgrade Exhaust System: Consider upgrading to a less restrictive exhaust system to improve airflow and performance.
  • Fine-Tune the Carburetor or Fuel Injection: After installation, carefully tune the carburetor or fuel injection system to achieve the optimal air/fuel mixture. This might require the use of a dyno or an air/fuel ratio gauge.
  • Break-In Period: Follow the manufacturer's recommended break-in procedure to allow the new components to properly seat and wear in.
  • Professional Installation (When in Doubt): If you're not comfortable performing the installation yourself, it's best to have it done by a qualified mechanic.

What About the Alternatives? Are There Other Ways to Boost Performance?

While a big bore kit is a popular option for increasing the power of a Rzr 170, it's not the only one. Here are a few alternatives:

  • Performance Exhaust System: A less restrictive exhaust system can improve airflow and increase horsepower.
  • High-Flow Air Filter: A high-flow air filter can also improve airflow and increase horsepower.
  • Clutch Kit: A clutch kit can improve acceleration and overall performance by optimizing the engagement and shift points.
  • ECU Tuning: For fuel-injected models, ECU tuning can optimize the fuel and ignition maps for increased performance.
  • Gear Ratio Changes: Changing the gear ratio can improve acceleration or top speed, depending on the chosen ratio.

These alternatives might not provide the same level of power gains as a big bore kit, but they are often easier to install and less likely to cause reliability problems. They can be a good option for those who are looking for a modest performance boost without the risks associated with a big bore kit.

Frequently Asked Questions

Q: Will a big bore kit void my warranty? A: Yes, installing a big bore kit will likely void your manufacturer's warranty, as it's considered an aftermarket modification.

Q: How much horsepower can I expect to gain with a big bore kit? A: Expect gains in the range of 20-30%, but this varies depending on the kit, tuning, and supporting modifications.

Q: Is a big bore kit difficult to install? A: It requires mechanical knowledge and attention to detail. Professional installation is recommended if you're not experienced.

Q: Do I need to upgrade my carburetor with a big bore kit? A: Most likely, yes. A larger displacement engine requires more fuel, so upgrading or re-jetting the carburetor is usually necessary.

Q: Will a big bore kit make my Rzr 170 less reliable? A: It can if not installed and maintained properly. Choosing quality components and careful tuning is crucial for long-term reliability.

The Bottom Line

A big bore kit can be a fantastic way to boost the performance of your Polaris Rzr 170, but it's crucial to understand the potential problems and take steps to avoid them. Careful planning, proper installation, and diligent maintenance are key to enjoying the benefits of increased power without sacrificing reliability. Weigh the pros and cons carefully before making a decision, and consider whether alternative performance upgrades might be a better fit for your needs and skill level.