Polaris Fst 750 Turbo Problems

So, you're the proud owner (or prospective owner) of a Polaris FST 750 Turbo. These machines were known for their impressive power and innovative technology, but like any complex piece of engineering, they weren't without their quirks. Knowing the potential pitfalls can save you a lot of headaches, time, and money down the road. Let's dive into the common issues that plagued the FST 750 Turbo and how you can tackle them.

Understanding the Beast: What Made the FST 750 Turbo Tick?

Before we jump into the problems, it's good to understand what made this snowmobile special. The FST 750 Turbo was Polaris's foray into forced induction in the snowmobile world. It featured a 750cc, four-stroke, twin-cylinder engine boosted by a turbocharger. This combination delivered impressive horsepower and torque, making it a popular choice for riders who craved performance. The "FST" stood for Four Stroke Turbo, highlighting the key technology. The engine management system was sophisticated for its time, but also contributed to some of the reliability concerns. It was a complex machine, and that complexity often translated to challenges.

The Elephant in the Room: Engine Reliability

Let's face it: the biggest concern surrounding the FST 750 Turbo was engine reliability. These engines weren't exactly known for their longevity, and a variety of factors contributed to their woes.

Overheating: One of the primary culprits was overheating. The turbocharger generated a lot of heat, and the cooling system wasn't always up to the task, especially in marginal snow conditions or when pushing the machine hard. This could lead to head gasket failures, piston damage, and even complete engine meltdown. Proper maintenance of the cooling system, including checking coolant levels, inspecting the radiator, and ensuring the cooling fan is functioning correctly, is crucial.
Oil Issues: The turbocharger relied heavily on proper oil lubrication. Oil starvation to the turbo could quickly lead to its demise, and contaminated or low oil could wreak havoc on the entire engine. Regular oil changes with high-quality synthetic oil were absolutely essential. Many owners opted for more frequent oil changes than recommended by Polaris to ensure optimal lubrication.
Fuel Delivery Problems: The fuel injection system, while advanced, could be finicky. Issues with fuel injectors, fuel pumps, or the fuel pressure regulator could lead to lean running conditions, which further exacerbated the overheating problem and could damage the engine.
Turbocharger Problems: The turbo itself was a potential source of issues. Bearing failures, boost leaks, and other turbo-related problems could significantly impact performance and reliability.

The Dreaded Detonation: A Knock at the Door

Detonation, also known as engine knock, was a common and destructive problem on the FST 750 Turbo. It occurs when the air-fuel mixture ignites prematurely in the cylinder, causing a violent pressure wave that can damage pistons, connecting rods, and other engine components.

Causes of Detonation: Detonation could be caused by a variety of factors, including:
- Lean Fuel Mixture: As mentioned earlier, lean running conditions were a major contributor.
- Low Octane Fuel: Using fuel with a lower octane rating than recommended by Polaris could trigger detonation. Always use premium fuel (91 octane or higher).
- Overheating: High engine temperatures increased the likelihood of detonation.
- Carbon Buildup: Carbon deposits in the combustion chamber could create hot spots that ignited the fuel prematurely.
Preventing Detonation: Preventing detonation required a multi-pronged approach:
- Ensuring Proper Fuel Delivery: Regularly inspect and clean the fuel injectors, check the fuel pump pressure, and ensure the fuel pressure regulator is functioning correctly.
- Using High-Quality Fuel: As mentioned, always use premium fuel.
- Maintaining the Cooling System: Keep the cooling system in top condition to prevent overheating.
- Decarbonizing the Engine: Periodically decarbonize the engine to remove carbon deposits.

Electrical Gremlins: Wiring and Sensors

Beyond the engine itself, the FST 750 Turbo could suffer from electrical problems.

Wiring Harness Issues: The wiring harness was known to be susceptible to chafing and damage, especially in areas where it rubbed against the chassis. This could lead to short circuits, intermittent failures, and other electrical gremlins.
Sensor Failures: Various sensors, such as the throttle position sensor (TPS), coolant temperature sensor, and boost pressure sensor, could fail, causing the engine to run poorly or not at all.
ECU Problems: In some cases, the electronic control unit (ECU) itself could develop problems, requiring replacement or reprogramming.

Transmission Troubles: Slipping and Sliding

The transmission on the FST 750 Turbo was generally reliable, but some issues could arise.

Belt Wear: Excessive belt wear was a common problem, especially when riding aggressively or in deep snow.
Clutch Issues: The clutches could wear out or develop problems, leading to slipping and poor performance. Regular inspection and maintenance of the clutches are essential.
Chain Case Problems: The chain case could suffer from leaks or bearing failures. Regular inspection and lubrication of the chain case are important.

Suspension and Chassis Concerns

While the focus is often on the engine, don't neglect the suspension and chassis.

Suspension Component Wear: Bushings, ball joints, and shocks could wear out over time, leading to poor handling and a rough ride.
Chassis Cracks: In some cases, the chassis could develop cracks, especially in areas that were subjected to high stress.

Tips for Keeping Your FST 750 Turbo Running Strong

Now that we've covered the common problems, let's talk about how to keep your FST 750 Turbo running smoothly.

Regular Maintenance: This is the single most important thing you can do. Follow the maintenance schedule in the owner's manual and be proactive about addressing potential problems.
Use High-Quality Fluids: Use high-quality synthetic oil, coolant, and fuel.
Monitor Engine Temperature: Keep a close eye on the engine temperature gauge and be prepared to stop if the engine starts to overheat.
Listen for Unusual Noises: Pay attention to any unusual noises coming from the engine or transmission. These could be early warning signs of a problem.
Don't Overboost: Avoid running the engine at excessively high boost levels, as this can put a strain on the engine and turbocharger.
Consider Aftermarket Upgrades: Some aftermarket upgrades, such as improved cooling systems and fuel controllers, can help to improve the reliability of the FST 750 Turbo.
Find a Good Mechanic: If you're not comfortable working on your snowmobile yourself, find a mechanic who is experienced with the FST 750 Turbo.

Frequently Asked Questions (FAQ)

Why are FST 750 Turbos known for being unreliable? The FST 750 Turbo had a complex engine with a turbocharger, increasing the risk of overheating, oiling issues, and detonation, leading to reliability concerns. Its cooling system was also often inadequate for the heat generated.
What kind of fuel should I use in my FST 750 Turbo? Always use premium fuel (91 octane or higher) to prevent detonation and ensure optimal performance. Using lower octane fuel can damage the engine.
How often should I change the oil in my FST 750 Turbo? While Polaris recommends a specific interval, many owners opt for more frequent oil changes (every 500-750 miles) with high-quality synthetic oil. This helps ensure proper turbocharger lubrication.
What are the signs of detonation? Signs of detonation include a knocking or pinging sound coming from the engine, especially under load. Ignoring these sounds can lead to severe engine damage.
Can I upgrade the cooling system on my FST 750 Turbo? Yes, aftermarket cooling system upgrades are available and can help to improve the reliability of the engine, especially in marginal snow conditions. These upgrades can include larger radiators and improved cooling fans.

The Final Run: Keeping the Legacy Alive

The Polaris FST 750 Turbo was a groundbreaking machine that pushed the boundaries of snowmobile technology. While it had its share of problems, with proper maintenance and attention, you can keep these machines running strong and enjoy their unique blend of power and performance. Don't be afraid to tackle the common issues, and remember that preventative maintenance is key to long-term reliability.