Choosing the Right Aftermarket Spark Plugs for the 1978-1994 Arctic Cat Cheetah 440
Keep your vintage Cheetah 440 running strong with the correct spark plugs.
- The most common replacement spark plug for the Cheetah 440 is the NGK BR9ES.
- Two-stroke engines like the one in the Cheetah 440 are prone to spark plug fouling, especially from too much idling.
- Upgrading to an Iridium plug like the NGK BR9EIX can provide longer life and better fouling resistance.
- Always carry spare plugs and the tools to change them when riding.
Signs of a Failing Spark Plug
A worn or fouled spark plug can cause a range of problems on your Cheetah 440. Two-stroke engines, in particular, are sensitive to spark plug condition. Letting the engine idle for too long or riding at consistently low speeds can increase the chances of fouling the plugs. It's a common issue, which is why most snowmobiles have a designated spot to carry spare plugs.
Common Symptoms
- Hard Starting: Difficulty getting the engine to fire up, especially when cold.
- Engine Misfires: The engine may sputter, pop, or run unevenly.
- Reduced Power: You'll notice the sled feels sluggish and doesn't accelerate like it should.
- Poor Fuel Economy: A weak spark leads to an incomplete burn, wasting fuel.
- Fouled Plugs: Upon inspection, the plug tip will be covered in black, sooty carbon or wet with oil and fuel.
Choosing the Right Aftermarket Spark Plug
For a vintage two-stroke like the Cheetah 440, selecting the correct spark plug is critical for performance and engine health. You have several options across different brands and material types. The most commonly recommended plug for this model range is the NGK BR9ES. This is a standard, reliable choice for millions of powersports vehicles.
Brand & Material Tiers
When shopping for a new spark plug, you'll see different materials mentioned. For this sled, the choice between them affects both performance and how often you'll need to change them.
| Tier | Brands & Materials | Price Range (per plug) | Best For |
|---|---|---|---|
| Good (Standard) | NGK, Champion (Copper/Nickel Alloy) | $3.91 - $8.00 | Standard replacement for regular trail riding. Copper plugs are excellent conductors and work very well in two-stroke engines, though they wear faster. Many owners stick with the OEM-style standard plug for reliability. |
| Better (Premium) | NGK, Denso (Iridium) | $10.00 - $33.95 | Riders looking for longer service life, improved starting, and better foul resistance. Iridium plugs have a fine-wire electrode that creates a more focused spark and resists wear better than copper. The NGK BR9EIX is a common iridium upgrade. |
Pro Tip: Always carry a spare set of plugs and a plug wrench when you ride. Two-stroke engines can foul plugs unexpectedly, and being able to swap them on the trail can save your day.
Frequently Asked Questions
What is the correct spark plug for my Cheetah 440?
The most frequently cited spark plug for the 1978-1994 Arctic Cat Cheetah 440 is the NGK BR9ES. This is a standard resistor plug. An iridium upgrade option is the NGK BR9EIX. Always confirm the specific plug for your exact year, as recommendations can vary slightly.
What does the 'R' in a spark plug number like BR9ES mean?
The 'R' stands for Resistor. Resistor plugs are designed to suppress electrical noise (Radio Frequency Interference) that can interfere with electronic components. Using a non-resistor plug where a resistor is specified could potentially cause issues with your sled's ignition system over time.
What is a spark plug's "heat range"?
The heat range (the '9' in BR9ES) indicates how quickly the plug transfers heat away from its firing tip. A lower number (like B8ES) is a "hotter" plug that retains more heat, while a higher number (like B9ES) is a "colder" plug that dissipates heat faster. Using a plug that is too hot can lead to engine damage, while a plug that is too cold can lead to carbon fouling. It is best to stick with the manufacturer's recommended heat range.
Are expensive iridium plugs worth it for my old sled?
It depends on your priorities. Standard copper plugs are affordable and work great, but may need more frequent changes. Iridium plugs cost more but offer a longer life, better resistance to fouling, and can provide easier starting. For many vintage sled owners, the reliability and longevity of iridium plugs are worth the extra cost.
Why does my Cheetah 440 keep fouling plugs?
Fouling on a two-stroke is common and can be caused by several factors. Excessive idling, running at low RPMs for long periods, an incorrect oil mixture, or a carburetor that is running too rich can all lead to fouled plugs. If you are fouling plugs constantly despite riding normally, it may indicate a mechanical issue like a weak spark or a problem with the carburetor.
Technical Specifications
The standard recommended plug is an NGK BR9ES. It has a 14mm thread, 19mm reach, and a 20.6mm or 21mm hex size. The 'B' indicates the thread size, 'R' means it's a resistor plug, '9' is the heat range, 'E' is the thread reach, and 'S' denotes a standard copper center electrode.
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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.