The Polaris Sportsman 850 Ultimate Trail is marketed as the pinnacle of off-road adventure, promising unparalleled performance and comfort on the toughest terrains. However, like any complex machine, it's not without its quirks and potential issues. Understanding these problems, and more importantly, how to address them, can significantly enhance your riding experience and prevent costly repairs down the line. This article delves into the most common problems reported by Sportsman 850 Ultimate Trail owners, offering practical solutions and preventative measures to keep you confidently exploring the trails.

So, You've Got an 850 Ultimate Trail – What Could Go Wrong?

While the Sportsman 850 Ultimate Trail is a robust ATV, several recurring issues have been documented by owners. These range from minor annoyances to more serious mechanical failures. Knowing what to look for is half the battle. Let's break down some of the most frequent complaints and how to tackle them.

The Dreaded EPS (Electronic Power Steering) Issues

One of the most common and frustrating problems reported with the Sportsman 850 Ultimate Trail is related to the Electronic Power Steering (EPS) system. This system is designed to make steering easier, especially at low speeds and on rough terrain. However, it can be prone to failure.

  • Symptoms: The most obvious symptom is a sudden loss of power steering assist. The steering wheel will become significantly harder to turn, especially at low speeds. You might also notice an EPS warning light illuminating on the dashboard. Intermittent power steering, where the assist cuts in and out, is another common sign.
  • Causes: Several factors can contribute to EPS failure. Low battery voltage is a frequent culprit. The EPS system requires a stable and sufficient power supply to function correctly. A weak or failing battery can cause the EPS to malfunction. Another common cause is a faulty EPS unit itself. Sensors within the unit can fail, leading to incorrect readings and loss of assist. Damaged wiring or connectors in the EPS system can also cause intermittent or complete failure.
  • Solutions: First, check your battery voltage. Ensure it's within the specified range (typically around 12.6V when the engine is off and 13.5-14.5V when the engine is running). If the battery is weak, replace it. Next, inspect the wiring and connectors associated with the EPS system. Look for any signs of corrosion, damage, or loose connections. Clean and tighten any suspect connections. If the problem persists, you may need to have the EPS unit diagnosed by a qualified mechanic. In some cases, the entire EPS unit may need to be replaced.

Hot, Hot, Hot! Overheating Problems

Overheating is another relatively common concern among Sportsman 850 Ultimate Trail owners, especially those who ride in hot climates or engage in demanding activities like mudding or rock crawling.

  • Symptoms: The temperature gauge on the dashboard will climb into the red zone. You might also notice steam emanating from the radiator or engine compartment. The engine may also exhibit reduced performance or even stall.
  • Causes: A clogged radiator is a primary suspect. Mud, debris, and even insects can accumulate in the radiator fins, restricting airflow and reducing its cooling efficiency. A low coolant level is another obvious cause. A faulty thermostat, which regulates coolant flow, can also lead to overheating. A malfunctioning cooling fan can also prevent adequate heat dissipation.
  • Solutions: Regularly clean your radiator with a garden hose, being careful not to damage the fins. Use a radiator fin comb to straighten any bent fins. Check your coolant level and top it off as needed. Ensure you're using the correct type of coolant recommended by Polaris. If the problem persists, have the thermostat and cooling fan checked by a mechanic. Consider installing a radiator guard to protect it from debris.

The Mysterious Misfire

Engine misfires can be a frustrating problem, causing rough running, reduced power, and poor fuel economy.

  • Symptoms: The engine may stumble or hesitate during acceleration. You might also feel vibrations or jerking while riding. The check engine light may illuminate.
  • Causes: A faulty spark plug is a common cause of misfires. A clogged fuel injector can also disrupt the fuel supply to the engine. A vacuum leak can introduce unmetered air into the engine, causing it to run lean and misfire. A faulty ignition coil can also prevent the spark plug from firing properly.
  • Solutions: Start by checking the spark plugs. Inspect them for wear, damage, or fouling. Replace them if necessary. Consider using a fuel injector cleaner to help clear any blockages in the fuel injectors. Check for vacuum leaks by listening for hissing sounds around the engine. Inspect vacuum hoses for cracks or damage. If the problem persists, have the ignition coils and fuel injectors professionally tested.

Brake Issues: Squealing and Grinding

Brake problems are not only annoying but also potentially dangerous. Squealing or grinding noises from the brakes are a common complaint.

  • Symptoms: Obvious squealing, grinding, or scraping noises when applying the brakes. Reduced braking performance.
  • Causes: Worn brake pads are the most common cause. Debris, such as mud or sand, can also become lodged between the brake pads and rotors, causing noise and reduced performance. Warped brake rotors can also cause vibrations and noise. A sticking brake caliper can cause the brakes to drag, leading to overheating and premature wear.
  • Solutions: Inspect your brake pads for wear. Replace them if they are worn down to the wear indicators. Clean the brake components with brake cleaner to remove any debris. Check the brake rotors for warping or damage. If necessary, have them resurfaced or replaced. Ensure the brake calipers are functioning properly and not sticking. Lubricate the caliper slides as needed.

The Throttle Position Sensor (TPS) Gremlin

The Throttle Position Sensor (TPS) plays a crucial role in regulating the engine's performance. A faulty TPS can lead to a variety of problems.

  • Symptoms: Erratic idling, hesitation during acceleration, and poor throttle response. The engine may also stall unexpectedly.
  • Causes: The TPS can become damaged or worn over time. It can also be affected by moisture or corrosion.
  • Solutions: Check the TPS wiring and connector for any signs of damage or corrosion. Try cleaning the TPS connector with electrical contact cleaner. If the problem persists, you may need to replace the TPS. It is recommended to have this calibrated by a professional to ensure proper engine performance.

Electrical Gremlins: A Constant Battle

ATVs, especially those with a lot of electronic components, can be prone to electrical issues.

  • Symptoms: Intermittent electrical problems, such as lights flickering, accessories not working, or the engine not starting.
  • Causes: Loose or corroded connections are a common cause. Damaged wiring can also lead to electrical problems. A faulty voltage regulator can cause overcharging or undercharging of the battery.
  • Solutions: Inspect all electrical connections for looseness or corrosion. Clean and tighten any suspect connections. Check the wiring harness for any signs of damage. Have the voltage regulator tested to ensure it's functioning properly.

Suspension Woes: Bushings and Bearings

The Sportsman 850 Ultimate Trail's suspension system is designed to provide a comfortable ride on rough terrain. However, the bushings and bearings in the suspension can wear out over time, leading to problems.

  • Symptoms: Squeaking or rattling noises from the suspension. Loose or sloppy handling. Excessive tire wear.
  • Causes: Worn or damaged bushings and bearings. Lack of lubrication.
  • Solutions: Regularly lubricate the suspension components with a high-quality grease. Inspect the bushings and bearings for wear or damage. Replace them as needed.

Frequently Asked Questions (FAQ)

  • Why is my Sportsman 850 overheating? Overheating can be caused by a clogged radiator, low coolant level, faulty thermostat, or malfunctioning cooling fan. Regularly clean your radiator and check your coolant level.
  • What causes EPS failure on the Sportsman 850? EPS failure can be caused by low battery voltage, a faulty EPS unit, or damaged wiring. Check your battery voltage and inspect the wiring for any damage.
  • My Sportsman 850 is misfiring. What could be the problem? Misfires can be caused by faulty spark plugs, clogged fuel injectors, vacuum leaks, or faulty ignition coils. Start by checking the spark plugs and consider using a fuel injector cleaner.
  • Why are my brakes squealing? Squealing brakes are often caused by worn brake pads or debris between the pads and rotors. Inspect your brake pads and clean the brake components.
  • What is the Throttle Position Sensor (TPS) and what happens if it fails? The TPS regulates the engine's performance. A faulty TPS can cause erratic idling, hesitation during acceleration, and poor throttle response.

Keeping Your Ultimate Trail Truly Ultimate

The Polaris Sportsman 850 Ultimate Trail is a capable and enjoyable machine, but understanding its potential problems and implementing preventative maintenance is crucial for maximizing its lifespan and your enjoyment. By addressing these common issues proactively, you can ensure that your adventures are filled with thrills, not frustrations. Remember, regular maintenance and addressing issues early are key to keeping your Sportsman 850 Ultimate Trail running smoothly for years to come.