Spark Plug Guide for the 1999-2002 ATK 50 MX
Get the right spark and keep your 50 MX running strong with this guide to new aftermarket spark plugs.
- The standard replacement plug is an NGK B7HS or equivalent; using a quality aftermarket brand is perfectly fine.
- The most common issue is spark plug fouling from too much idling or a rich fuel mixture, not a defective plug.
- Changing the spark plug is an extremely easy DIY job that takes less than 15 minutes.
- Keep a spare plug on hand for quick trail-side fixes.
Signs of a Failing Spark Plug
A bad spark plug is one of the most common reasons for a 2-stroke engine to run poorly. Because the ATK 50 MX is a youth model, it often sees a lot of low-speed riding and idling, which can cause issues. Watch for these signs:
- Hard Starting: The bike is difficult to kick over or won't start at all. This is the most common symptom.
- Engine Misfires or Sputtering: The engine cuts out or hesitates during acceleration.
- Rough Idle: The engine doesn't run smoothly when you're not on the throttle.
- Fouling: If you remove the plug, it may be coated in a black, sooty, or oily substance. This is known as spark plug fouling and it prevents a strong spark.
The Real Issue: Spark Plug Fouling
For the ATK 50 MX, the problem is almost always a fouled plug, not a defective one. Fouling happens when unburnt fuel, oil, and carbon build up on the plug's tip. This is common in 2-strokes from too much idling, an incorrect fuel/oil mix, or a carburetor that is running too rich (too much fuel, not enough air). Simply replacing the plug will fix it temporarily, but addressing the root cause is key.
Choosing the Right Aftermarket Spark Plug
For a standard replacement, you don't need to hunt down a specific "OEM" plug. High-quality aftermarket brands are excellent and readily available. The most important factor is getting the correct part number with the right heat range and size. The standard plug for the 1999-2002 ATK 50 MX is an NGK B7HS or an equivalent from another brand.
Brand Tiers for Your ATK 50 MX
- Top Tier (OEM Equivalent): NGK and Denso are Japanese brands known for being original equipment on many motorcycles. They offer outstanding reliability and performance. For the 50 MX, an NGK is often considered the default choice.
- Trusted Aftermarket: Champion is a well-known American brand that produces reliable plugs. A compatible Champion plug like the RL82C is a solid, budget-friendly choice that will perform well.
- Performance Plugs (Iridium): Brands like NGK and Denso offer iridium plugs. These have a longer lifespan and can provide a more consistent spark. However, for a 50cc 2-stroke, the performance gain is minimal and may not be worth the extra cost, especially since fouling from riding habits or tuning is the more likely issue.
Pro Tip: Buy two or three spark plugs at a time. They are inexpensive, and having a fresh plug on hand is the quickest way to solve a fouling issue when you're out riding.
Aftermarket Spark Plug Cost for ATK 50 MX
| Brand Type | Our Price Range | Notes |
|---|---|---|
| Standard Copper (NGK, Champion, Denso) | $3.61 - $8.00 | The best value. Excellent performance for this engine. |
| Iridium (NGK IX, Denso Iridium) | $9.00 - $17.05 | Longer life, but not necessary for most riders of this bike. |
Frequently Asked Questions
How often should I change the spark plug?
On a 2-stroke dirt bike, it's best to inspect the spark plug every 10-15 hours of riding and replace it if it looks fouled or worn. Given their low cost, many owners replace them at the start of each riding season or every 20-30 hours regardless of appearance.
What is the correct spark plug gap for the ATK 50 MX?
The standard spark plug gap is 0.7mm or 0.028 inches. Most plugs come pre-gapped, but it's always a good idea to check with a feeler gauge before installation.
What does the 'R' mean in a spark plug model like BR7HS?
The 'R' stands for Resistor. A resistor spark plug helps suppress radio frequency interference (RFI) that can affect electronic components. While the standard B7HS is a non-resistor plug, using a BR7HS is perfectly fine and sometimes recommended.
Can I clean a fouled spark plug?
Yes, you can temporarily clean a fouled plug. Use a wire brush and some brake cleaner to remove carbon deposits from the electrode and insulator. However, this is often a temporary fix, and since new plugs are so inexpensive, replacement is usually the better option.
Technical Specifications
OEM Part Numbers: NGK B7HS NGK BR7HS Champion RL82C
Thread Reach: 12.7mm, Hex Size: 20.6mm (13/16"), Heat Range: 7, Spark Gap: 0.7mm (0.028").
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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.
- ATK 50 MX: