Spark Plug Guide for the 1974-1981 Arctic Cat Cheetah 340
Keep your vintage Cheetah 340 running strong with the right set of spark plugs.
- The standard recommended spark plug is the NGK B8ES. A premium upgrade is the NGK Iridium BR8EIX for better performance and longevity.
- Always replace spark plugs in pairs to ensure balanced engine performance.
- Check the spark plug gap before installation. The target is 0.8 mm (0.031").
- No recalls or technical service bulletins related to spark plugs are known for this vintage vehicle.
Signs of a Failing Spark Plug
Worn or fouled spark plugs can cause a number of noticeable problems in your Cheetah 340. Because the engine relies on a clean spark, even minor issues with the plug can affect performance. Look out for these common symptoms:
- Hard Starting: A weak spark makes it difficult to ignite the fuel mixture, especially when the engine is cold.
- Engine Misfires: You might feel the engine stumble or hesitate during acceleration. This is often due to an inconsistent spark.
- Rough Idle: A fouled or worn plug can cause the engine to run unevenly at idle.
- Loss of Power: If the spark isn't strong enough to burn all the fuel efficiently, your sled will feel sluggish and less powerful.
- Increased Fuel Consumption: Inefficient combustion means you'll be burning through more fuel than usual.
Reading the Plugs
🎬 Watch: How to read your spark plugs for engine health.The condition of your old spark plugs can tell you a lot about your engine's health. A light tan or grayish-brown color on the insulator nose is normal. A black, sooty plug can indicate a rich fuel mixture or excessive idling. A wet, oily plug can be a sign of more serious engine issues.
Choosing the Right Aftermarket Spark Plug
For a vintage machine like the 1974-1981 Cheetah 340, aftermarket spark plugs are the standard. The original OEM plugs were likely made by one of these major brands anyway. Your choice comes down to material and brand reputation.
Brand & Quality Tiers
Tier 1: Premium (Iridium)
- NGK Iridium (BR8EIX): Iridium plugs offer the best performance and longest life. They have a fine-wire center electrode that creates a more focused and consistent spark, which can improve starting and throttle response. While more expensive, they are highly resistant to wear and fouling.
Tier 2: Standard (Copper/Nickel)
- NGK Standard (B8ES): This is the workhorse plug and the most commonly cited standard replacement for the Cheetah 340. It provides reliable performance at a very affordable price. It is a non-resistor plug.
- Denso Standard (W24ES-U): Denso is a highly respected Japanese brand, and the W24ES-U is their direct equivalent to the NGK B8ES, offering similar performance and reliability.
- Champion Standard (N2C / RN3C): Champion is a classic American brand. The N2C is a non-resistor equivalent to the B8ES. The RN3C is a resistor plug, making it an alternative to the NGK BR8ES. Both are dependable choices for standard use.
Resistor vs. Non-Resistor Plugs
Resistor plugs (like NGK BR8ES or Champion RN3C) are designed to suppress radio frequency interference (RFI) that can affect electronic equipment. Non-resistor plugs (like NGK B8ES or Champion N2C) do not have this feature. For a vintage sled without sensitive electronics, a non-resistor plug is perfectly fine and often preferred for the strongest possible spark.
Aftermarket Spark Plug Cost for 1974-1981 Arctic Cat Cheetah 340
| Category | Price Range (Per Plug) | Notes |
|---|---|---|
| Standard Aftermarket (NGK, Denso, Champion) | $3.76 - $10.00 | This is the most common and affordable option. Includes plugs like the NGK B8ES. |
| Premium Aftermarket (Iridium) | $10.00 - $55.77 | Includes high-performance plugs like the NGK BR8EIX for improved longevity and spark quality. |
Frequently Asked Questions
How often should I change the spark plugs on my Cheetah 340?
For a vintage two-stroke engine, it's good practice to inspect your plugs every 20-30 hours of operation and replace them at the beginning of each riding season, regardless of appearance. They are inexpensive and critical for reliability.
What is the correct spark plug gap?
The recommended spark plug gap for the NGK B8ES is 0.8 mm (or approximately 0.031 inches). 🎬 See this quick guide on how to gap a spark plug. Always double-check the gap with a feeler gauge before installation, as it can shift during shipping.
Is it worth upgrading to an iridium spark plug?
For many riders, yes. Iridium plugs like the NGK BR8EIX provide a more consistent spark, can make starting easier, and last much longer than standard copper plugs. If you want the best possible performance and reliability, the extra cost is often justified.
Do I need to replace both spark plugs at the same time?
Yes. Your Cheetah 340 has a two-cylinder engine, and you should always replace both spark plugs as a set. 🎬 Watch: How to change the spark plugs on your snowmobile. This ensures balanced performance between the cylinders.
Helpful Videos
Technical Specifications
{ "Standard Plug": "NGK B8ES", "Thread Diameter": "14.0 mm", "Thread Length": "19.0 mm", "Wrench Size": "20.8 mm (or 21mm)", "Recommended Gap": "0.8 mm (0.031 in)", "Cross References (Standard)": "Denso W24ES-U, Champion N2C", "Cross References (Resistor)": "NGK BR8ES, Champion RN3C" }
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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.