The Polaris Cleanfire 800 HO engine, a powerhouse in its day, powered many snowmobiles and ATVs to adrenaline-pumping adventures. But like any complex machine, it wasn't without its quirks. Understanding the potential problems with this engine can save you time, money, and a whole lot of frustration out on the trail.

A Quick Look at the Polaris Cleanfire 800 HO

Before diving into the nitty-gritty, let's quickly recap what made the Cleanfire 800 HO special. It was designed to deliver strong performance and improved fuel efficiency compared to its predecessors. However, it also introduced some new technologies that, while innovative, could sometimes lead to issues. This isn't to say it was a bad engine - far from it! But knowing its potential weaknesses is crucial for any owner or prospective buyer.

The Elephant in the Room: Piston Failures

Piston failures are probably the most notorious problem associated with the Polaris Cleanfire 800 HO. These failures often manifest as a sudden loss of power, accompanied by unpleasant noises. Here's what typically causes them:

  • Lean Fuel Mixture: The engine needs the correct amount of fuel to cool the piston. A lean mixture (too little fuel, too much air) can cause the piston to overheat and eventually fail. This can be caused by faulty fuel injectors, a clogged fuel filter, or air leaks in the intake system.
  • Detonation/Pre-Ignition: This occurs when the fuel mixture ignites prematurely or uncontrollably. This can damage the piston crown.
  • Poor Quality Fuel: Using low-octane fuel or fuel contaminated with water or other substances can lead to improper combustion and piston damage.
  • Insufficient Oil: Proper lubrication is vital for piston health. A lack of oil can cause excessive friction and heat, leading to seizure and failure. Problems with the oil pump or oil lines can cause this.
  • Manufacturing Defects: Although less common, manufacturing flaws in the pistons themselves can contribute to premature failure.

How to avoid piston failure:

  • Use High-Quality Fuel: Always use the recommended octane rating and ensure your fuel is fresh and clean.
  • Maintain Proper Oil Levels: Regularly check and maintain your oil level. Consider using a high-quality synthetic oil designed for two-stroke engines.
  • Inspect Fuel System Components: Regularly check your fuel filter, fuel lines, and fuel injectors for any signs of clogs or leaks.
  • Consider Fuel Controller Adjustments: Some owners choose to install fuel controllers to fine-tune the fuel mixture and ensure adequate lubrication, especially at higher elevations or during aggressive riding.
  • Regular Compression Tests: Perform regular compression tests to monitor the health of your pistons. A significant drop in compression can indicate a problem.

The Dreaded Crankshaft Issues

The crankshaft is the backbone of the engine, and unfortunately, it can also be a weak point in the Cleanfire 800 HO.

  • Crankshaft Bearing Failures: The bearings that support the crankshaft can fail due to lack of lubrication, overheating, or excessive stress. This can lead to crankshaft damage and ultimately, engine failure.
  • Crankshaft Runout: Crankshaft runout refers to the degree to which the crankshaft is bent or out of alignment. Excessive runout can cause vibration, bearing wear, and ultimately, crankshaft failure.

How to Mitigate Crankshaft Problems:

  • Proper Lubrication: Ensuring the crankshaft bearings are properly lubricated is crucial. Use the recommended oil and maintain the oil injection system.
  • Regular Inspection: Periodically inspect the crankshaft for any signs of wear or damage. Listen for unusual noises that could indicate a problem.
  • Professional Maintenance: If you suspect a crankshaft issue, seek professional help. Replacing or rebuilding a crankshaft is a complex task that requires specialized tools and knowledge.
  • Consider a Crankshaft Upgrade: When rebuilding the engine, consider upgrading to a stronger, more durable crankshaft.

Dealing with Detonation and Pre-Ignition

As mentioned earlier, detonation and pre-ignition are significant threats to the health of the Cleanfire 800 HO.

  • Detonation: This occurs when the fuel-air mixture explodes uncontrollably after the spark plug has fired. It creates shockwaves that can damage pistons, cylinders, and connecting rods.
  • Pre-Ignition: This happens when the fuel-air mixture ignites before the spark plug fires. This is often caused by hot spots in the combustion chamber, such as carbon deposits or overheated spark plugs.

Battling Detonation and Pre-Ignition:

  • Use High-Octane Fuel: High-octane fuel is more resistant to detonation and pre-ignition.
  • Maintain Proper Cooling: Ensure the engine is properly cooled. Overheating can increase the risk of detonation and pre-ignition. Check your coolant levels and ensure the cooling system is functioning correctly.
  • Proper Spark Plug Selection: Use the correct spark plugs for your engine. Incorrect spark plugs can overheat and cause pre-ignition.
  • Clean Combustion Chamber: Regularly clean the combustion chamber to remove carbon deposits, which can create hot spots and cause pre-ignition.

The Electronic Gremlins: Sensors and Wiring

Like modern engines, the Cleanfire 800 HO relies on a network of sensors and wiring to operate efficiently. However, these components can be prone to failure.

  • Throttle Position Sensor (TPS) Issues: A faulty TPS can cause erratic engine performance, poor fuel economy, and even engine stalling.
  • Crankshaft Position Sensor (CPS) Problems: The CPS is critical for timing the ignition. A faulty CPS can cause the engine to run poorly or not start at all.
  • Wiring Harness Problems: Damaged or corroded wiring can cause a variety of electrical problems, including sensor malfunctions, short circuits, and complete engine failure.

Keeping the Electronics Happy:

  • Regular Inspection: Regularly inspect the wiring harness for any signs of damage or corrosion.
  • Proper Storage: Store your snowmobile or ATV in a dry place to prevent corrosion.
  • Use Dielectric Grease: Apply dielectric grease to electrical connections to prevent corrosion and improve conductivity.
  • Professional Diagnosis: If you suspect an electrical problem, seek professional help. Diagnosing electrical issues can be challenging and requires specialized tools and knowledge.

Exhaust Valve Problems

The Cleanfire 800 HO uses exhaust valves to optimize engine performance at different RPMs. These valves can sometimes stick or malfunction.

  • Carbon Buildup: Carbon buildup on the exhaust valves can cause them to stick, which can lead to reduced performance and poor fuel economy.
  • Actuator Problems: The actuators that control the exhaust valves can fail, preventing the valves from opening and closing properly.

Tackling Exhaust Valve Issues:

  • Regular Cleaning: Regularly clean the exhaust valves to remove carbon buildup. There are specialized cleaners available for this purpose.
  • Inspect Actuators: Inspect the actuators for any signs of damage or wear.
  • Proper Lubrication: Ensure the exhaust valves are properly lubricated.

Frequently Asked Questions

  • Why did my Polaris 800 HO engine fail? It could be due to a lean fuel mixture, detonation, poor lubrication, or component failure like pistons or crankshaft.
  • What fuel should I use in my Polaris 800 HO? Always use the fuel octane rating recommended by Polaris, typically premium (91 octane or higher).
  • How often should I change the oil in my Polaris 800 HO? Follow the manufacturer's recommendations in the owner's manual, usually every season or after a certain number of miles.
  • Is the Polaris 800 HO engine reliable? With proper maintenance and careful operation, it can be reliable, but it's known for potential issues like piston and crankshaft failures.
  • Can I prevent piston failure on my Polaris 800 HO? Yes, by using high-quality fuel and oil, maintaining the fuel system, and performing regular maintenance.
  • How do I check the compression on my Polaris 800 HO? Use a compression tester and follow the service manual instructions. Low compression indicates potential engine problems.
  • What does "HO" stand for in Polaris Cleanfire 800 HO? "HO" stands for High Output, indicating a performance-oriented version of the engine.

Final Thoughts

The Polaris Cleanfire 800 HO engine, while powerful and exciting, requires careful attention and maintenance to avoid potential problems. By understanding the common issues and taking proactive steps to prevent them, you can keep your machine running strong for years to come.