Essential Spark Plug Guide for the 2008-2009 Arctic Cat 366 4x4 Auto
Keep your ATV's single-cylinder engine firing properly with the right spark plug.
- The recommended OEM-equivalent spark plug is the NGK CR8E.
- Symptoms of failure are very noticeable in the single-cylinder 366 engine, including hard starting and rough idling.
- Replacement is a simple, beginner-friendly DIY task that takes less than 15 minutes.
- Always verify the spark plug gap is 0.7 mm before installation.
Signs of a Failing Spark Plug
Your Arctic Cat 366's engine will usually let you know when its spark plug is wearing out. Because it's a single-cylinder engine, the effects of a bad plug are often more obvious than on a multi-cylinder machine. Look out for these common symptoms:
- Hard Starting: Difficulty getting the engine to turn over is one of the most common signs. A weak spark struggles to ignite the fuel mixture, especially in cold weather.
- Rough Idling: If the engine sputters, vibrates excessively, or sounds uneven at idle, the spark plug may be fouled or worn.
- Poor Acceleration: A noticeable loss of power or hesitation when you press the throttle points to an inconsistent spark.
- Engine Misfires: A misfire feels like a stumble or a jerk from the engine during operation. This happens when the plug fails to ignite the fuel in the cylinder.
- Increased Fuel Consumption: An inefficient spark leads to incomplete fuel combustion, meaning you'll be stopping for gas more often.
Known Issues & Recalls
As of early 2026, there are no specific recalls or Technical Service Bulletins (TSBs) from Arctic Cat or the NHTSA related to the spark plugs on the 2008-2009 366 4x4 Auto. Problems are typically due to normal wear and tear.
Choosing the Right Aftermarket Spark Plug
The original equipment (OEM) spark plug for the 366 is an NGK CR8E. Aftermarket brands offer direct-fit replacements that often meet or exceed OEM quality. For this ATV, sticking with a reputable brand is key.
Brand Tiers for Your Arctic Cat:
- Top Tier (Recommended): NGK is the OEM choice and a trusted standard for a reason. Their standard CR8E plug is the workhorse for this engine. Denso is another top-quality Japanese brand offering equivalent performance and reliability. You can't go wrong with either for consistent performance.
- Mid Tier: Champion plugs are a well-known American brand. While they produce reliable plugs, owner feedback and OEM specification point more strongly towards NGK for this specific Arctic Cat model. They are a perfectly acceptable alternative if your local shop stocks them.
Cost of a New Spark Plug
Spark plug replacement is one of the most affordable maintenance jobs you can do. The cost depends on the plug material (standard nickel, platinum, or iridium) and the brand.
| Part Type | Typical Price Range |
|---|---|
| New Aftermarket (Standard) | $10 - $20 |
| New Aftermarket (Iridium/Premium) | $20 - $58 |
| New OEM (NGK) | $15 - $30 |
Frequently Asked Questions
How often should I change the spark plug on my Arctic Cat 366?
For a standard spark plug, it's good practice to inspect it annually and replace it every 1-2 years or as recommended in your owner's manual, depending on your riding hours and conditions. A fouled or worn plug should be replaced immediately.
Is it hard to change the spark plug myself?
No, this is a very easy DIY job. It requires basic tools like a spark plug socket and a ratchet. The plug is located on the top of the engine and is usually easy to access. Just be careful not to cross-thread the new plug when installing it—thread it in by hand first.
What is the correct spark plug for my 2008-2009 Arctic Cat 366?
The standard recommended plug is the NGK CR8E. Many aftermarket brands like Denso and Champion offer direct cross-reference replacements. You can also upgrade to an iridium version like the NGK CR8EIX for better longevity.
Do I need to gap a new spark plug?
Yes, you should always check the gap before installation, even if the plug is advertised as "pre-gapped." The correct gap for the standard plug is 0.7 mm. A feeler gauge is the right tool for this job.
Technical Specifications
OEM Part Numbers: 0217-708
Recommended Plug: NGK CR8E. Thread Diameter: 10mm. Wrench Size: 16mm. Spark Gap: 0.7mm.
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The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
- Arctic Cat 366 4x4 Auto: