The Polaris Fusion 700, released in the mid-2000s, promised a new era of snowmobiling with its revolutionary chassis and powerful engine. However, the Fusion quickly became notorious for a range of issues, leaving many riders stranded and frustrated. Understanding these problems is crucial for anyone owning, considering purchasing, or working on these machines.

The Fusion's Rocky Start: What Went Wrong?

The Polaris Fusion 700 debuted with high expectations, aiming to blend performance and handling in a single package. But almost immediately, problems began to surface, tarnishing its reputation and leading to significant warranty claims. The combination of a brand-new chassis design and a somewhat unrefined engine created a perfect storm of issues that plagued the Fusion throughout its production run.

Early adopters often faced the brunt of these problems, as initial production models were particularly prone to defects. Many of the issues stemmed from the rushed production schedule and the inherent challenges of introducing a completely new platform. This led to a steep learning curve for both Polaris and its customers.

The Dreaded Detonation: Engine Woes Explained

One of the most significant and talked-about problems with the Polaris Fusion 700 was detonation. This destructive phenomenon occurs when the air/fuel mixture in the cylinder ignites spontaneously, rather than from the spark plug. Detonation creates extreme pressure and heat, which can quickly lead to engine damage, including piston failure, cylinder head damage, and even complete engine seizure.

Several factors contributed to the Fusion 700's detonation issues:

  • Lean Fuel Mapping: The factory fuel injection mapping was often too lean, especially at higher altitudes or under heavy loads. A lean mixture burns hotter, increasing the risk of detonation.
  • Poor Cooling: The cooling system design on some Fusion 700 models was inadequate, especially in marginal snow conditions. Overheating further exacerbated the detonation problem.
  • Fuel Quality: Using lower-octane fuel than recommended could also trigger detonation. The engine was designed to run on premium fuel, and using anything less increased the risk.

The sound of detonation is often described as a metallic pinging or knocking sound coming from the engine. If you hear this while riding, it's crucial to stop immediately and address the issue to prevent further damage.

Chassis Cracks: A Structural Weakness

Beyond engine problems, the Polaris Fusion 700 also suffered from structural weaknesses in its chassis. Cracking was a common issue, particularly in high-stress areas like the tunnel and around the suspension mounting points.

  • Tunnel Cracking: The tunnel, which forms the backbone of the snowmobile, was prone to cracking, especially in the rear section. This could compromise the structural integrity of the entire machine.
  • Suspension Mounts: The suspension mounting points were also vulnerable to cracking, particularly under aggressive riding conditions. This could lead to instability and handling problems.

These chassis cracks were often attributed to the lightweight design of the Fusion's chassis, combined with the stresses of aggressive riding and rough terrain. While Polaris attempted to address these issues with reinforcement kits and updated designs, the problem persisted to some extent throughout the Fusion's production run.

Electrical Gremlins: A Troubleshooting Nightmare

Electrical problems were another common complaint among Polaris Fusion 700 owners. These issues ranged from minor annoyances to major malfunctions that could leave riders stranded.

  • Voltage Regulator Failure: The voltage regulator was a known weak point, often failing and causing erratic electrical behavior, including dim headlights, battery drain, and even complete electrical system shutdown.
  • Wiring Harness Issues: The wiring harness was also prone to chafing and corrosion, leading to intermittent electrical problems and shorts.
  • Sensor Failures: Various sensors, such as the throttle position sensor (TPS) and the coolant temperature sensor, could fail, causing engine performance problems and diagnostic trouble codes (DTCs).

Troubleshooting electrical problems on the Fusion 700 could be a challenge, often requiring specialized diagnostic tools and a thorough understanding of the electrical system. A multimeter and a wiring diagram were essential tools for diagnosing these issues.

Suspension Setups: Finding the Sweet Spot

While not necessarily a "problem" in the same way as engine detonation or chassis cracks, the Polaris Fusion 700's suspension setup was often criticized for being difficult to dial in. Many riders found it challenging to achieve a comfortable and predictable ride, especially in rough terrain.

  • Stiff Ride: The stock suspension settings were often too stiff, resulting in a harsh ride, particularly on bumpy trails.
  • Poor Handling: Some riders also complained about poor handling, including excessive body roll and a tendency to dart.

Experimenting with different suspension settings, such as adjusting the preload on the shocks and the limiter straps, was often necessary to find a setup that worked best for individual riding styles and conditions. Aftermarket suspension components, such as upgraded shocks and springs, could also improve the ride quality and handling.

What Can You Do? Solutions and Preventive Measures

While the Polaris Fusion 700 had its share of problems, many of these issues can be addressed with proper maintenance, modifications, and riding techniques.

  • Fuel Mapping Adjustments: Installing a fuel controller, such as a Dynojet Power Commander, allows you to fine-tune the fuel mapping and ensure a richer mixture, reducing the risk of detonation.
  • Cooling System Upgrades: Installing additional cooling components, such as a tunnel cooler or scratchers, can help keep the engine cool, especially in marginal snow conditions.
  • Chassis Reinforcement: Reinforcing the chassis with aftermarket kits can help prevent cracking, particularly in high-stress areas.
  • Regular Maintenance: Performing regular maintenance, such as checking the spark plugs, cleaning the fuel injectors, and inspecting the wiring harness, can help prevent problems before they occur.
  • Proper Riding Techniques: Avoiding prolonged high-speed runs in marginal snow conditions can help prevent overheating and detonation.

By taking these steps, you can significantly improve the reliability and longevity of your Polaris Fusion 700.

The Silver Lining: Why Some Riders Still Love the Fusion

Despite its problems, the Polaris Fusion 700 still has a loyal following among some riders. Its powerful engine, aggressive styling, and unique chassis design appeal to those who are willing to put in the effort to address its shortcomings.

  • Powerful Engine: When running properly, the Fusion 700's engine delivers impressive performance, with plenty of power and torque.
  • Aggressive Styling: The Fusion's bold and distinctive styling sets it apart from other snowmobiles.
  • Unique Chassis Design: The Fusion's chassis, while prone to cracking, offered a unique riding experience that some riders found appealing.

For those who are willing to invest the time and money into addressing its problems, the Polaris Fusion 700 can be a rewarding and enjoyable snowmobile.

Frequently Asked Questions

  • Why does my Fusion 700 keep detonating? Lean fuel mapping, poor cooling, and low-octane fuel can all contribute to detonation. Consider a fuel controller and cooling system upgrades.
  • Where are the most common places for the chassis to crack? The tunnel, especially in the rear, and the suspension mounting points are common areas for cracks. Regular inspection and reinforcement can help.
  • What are the symptoms of a failing voltage regulator? Dim headlights, battery drain, and erratic electrical behavior are common symptoms. A multimeter can be used to test the regulator.
  • How can I improve the ride quality of my Fusion 700? Experiment with different suspension settings and consider aftermarket shocks and springs. Finding the right setup can significantly improve comfort.
  • Is the Polaris Fusion 700 worth buying? It depends. If you are willing to address its known problems and perform regular maintenance, it can be a rewarding snowmobile.

In conclusion, the Polaris Fusion 700 had its share of problems, but understanding these issues and taking proactive steps can help you enjoy this unique and powerful snowmobile. Prioritizing proper maintenance and addressing known weaknesses is the key to a reliable ride.