Choosing the Right Spark Plug for Your 1986-1990 Arctic Cat Panther 340
Keep your vintage Panther 340 running reliably with the correct new aftermarket spark plugs.
- The standard recommended aftermarket spark plug is the NGK BR8ES.
- Always check and set the spark plug gap to approximately 0.8 mm before installation.
- Replacing spark plugs annually is cheap insurance against being stranded with a no-start condition.
- The color of the old spark plug can help diagnose other potential engine issues, like a rich or lean fuel mixture.
Signs of a Failing Spark Plug
A worn or fouled spark plug can cause several noticeable problems with your Panther 340's engine. Because the engine has two cylinders, a problem with one plug might make the sled feel like it's running on half power. Look for these common symptoms:
- Hard Starting: The engine cranks but struggles to fire up, especially when cold.
- Rough Idle: The engine idles unevenly or sounds like it's about to stall.
- Engine Misfires: You may hear a popping or sputtering sound from the exhaust as the engine misses a combustion cycle.
- Loss of Power: The snowmobile feels sluggish and doesn't accelerate as it should.
- Increased Fuel Consumption: An inefficient spark leads to wasted fuel.
- Fouled Plugs: If you remove the plug, it might be covered in black, sooty carbon or oily residue. This indicates a problem with the spark or fuel mixture.
Reading Your Spark Plugs
The color of your spark plug's tip can tell you a lot about your engine's health. A light tan or grayish-brown color indicates a healthy engine. A black, sooty plug suggests the fuel mixture is too rich or the spark is weak. A white or blistered plug means the engine is running too hot or lean, which can cause serious damage.
Choosing the Right Aftermarket Spark Plug
For a vintage machine like the 1986-1990 Panther 340, you don't need to hunt down a rare original part. High-quality aftermarket spark plugs are readily available and often made by the same companies that supplied the original parts. The most important factor is choosing the correct plug with the right heat range and specifications.
Brand Tiers & Recommendations
Tier 1: Recommended Aftermarket (OEM-Equivalent)
- NGK: NGK is the most widely recommended and used spark plug brand for vintage two-stroke snowmobiles. The standard plug for this application is the NGK BR8ES. This is a resistor plug, which is recommended to prevent electrical noise that could interfere with other components. You can rely on this plug for consistent performance and durability.
- Champion: Champion is another reputable brand that offers equivalent plugs, such as the RN2C. They are a dependable alternative if NGK plugs are not available.
Tier 2: Premium Aftermarket
- NGK Iridium (BR8EIX, BR9EIX): Iridium plugs offer a longer lifespan and a more consistent spark, especially in demanding conditions. They have a higher price but can be a good upgrade for riders looking for the best possible performance and longevity. The BR9EIX is a "colder" plug, which can be beneficial if you do a lot of high-speed riding.
Resistor vs. Non-Resistor Plugs
The recommended plug is a BR8ES, where the 'R' stands for resistor. While your Panther 340 doesn't have a complex computer, using a resistor plug is a safe bet to prevent any radio frequency interference. A non-resistor plug (like the B8ES) will work, but the resistor version is the standard and recommended choice.
Estimated Costs for Spark Plugs
| Part Type | Estimated Cost (per plug) | Notes |
|---|---|---|
| New Aftermarket (Standard Copper) | $3 - $8 | NGK BR8ES or Champion equivalent. Excellent value and performance. |
| New Aftermarket (Iridium) | $10 - $20 | NGK BR8EIX. Longer life and improved spark consistency. |
| Shop Labor | $25 - $50 | This is a very quick job, so labor should be minimal if you have a shop do it. |
Frequently Asked Questions (FAQ)
How often should I change the spark plugs on my Panther 340?
For a vintage two-stroke, it's good practice to inspect your spark plugs every season and replace them if they show any signs of wear or fouling. Given their low cost, many owners simply replace them at the start of each winter to ensure reliability.
What does the '8' in BR8ES mean?
The number in an NGK spark plug's name indicates its heat range. With NGK, a lower number means a hotter plug, while a higher number means a colder plug. The '8' heat range is the standard recommendation for the Panther 340's engine under normal use.
Do I need to gap the new spark plugs?
Yes, you should always check the gap before installation. The recommended gap for an NGK BR8ES is typically 0.8 mm (or 0.032 inches). Use a spark plug gapping tool to gently adjust the ground electrode if needed.
Can I use a hotter or colder spark plug?
You should stick with the manufacturer's recommended heat range (NGK '8') for general riding. If you do extended high-speed riding, a colder plug (like a BR9ES) might prevent overheating. Conversely, if you only do very slow, low-RPM riding and your plugs are fouling, a hotter plug (BR7ES) might help, but this often points to other issues like an incorrect fuel mixture. It's best to use the standard plug unless you have a specific tuning reason to change.
Technical Specifications
Recommended Plug: NGK BR8ES Thread Diameter: 14mm Wrench Size: 20.8mm (13/16") Gap: 0.8mm (0.032")
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 Panther 340: