The has recently been quite a bit of discussion locally, regarding counterfeit (fake) NGK spark plugs. Those of concern to me, as a classic motorcycle enthusiast, are the B6ES, B7ES and B8ES varieties which are used on my bikes.

A selection of NGK Spark Plugs

Before I start, the best way to avoid these counterfeit plugs is to buy from a reputable dealer such as AV Taylor is my area; it’s likely they will only buy from recognised and authorised NGK suppliers.

If you simply do an search using Google or Bing etc., for ‘how to spot counterfeit NGK spark plugs’ you’ll also get plenty of information back.

The problem with counterfeit plugs is that they are not manufactured well at all.

  • quality will be poor
  • the heat rating won’t match that which your engine requires
  • they will probably be fitted with an internal resistor
  • the insulation will be poor
  • worst of all, they can fall apart, destroying the top end of your engine and more

Initially, test the resistance from the top cap of your plug to the central conductor at the plug tip; it should be zero, unless it’s designed to have a resistor fitted. The problem is, that the counterfeiters initially make them all the same, then add markings to make them appear different.

When the counterfeit plugs originally hit the market, not everyone was aware that they were fake…the result was that NGK’s reputation was tarnished badly.

Rather than rewrite it, here’s what Google’s AI had to say about the issue:

To spot counterfeit (fake) NGK motorcycle spark plugs, carefully inspect the printing and font on the box and plug for blurriness or errors, check for the correct EAC certification logo on the packaging, and examine the plug itself for poor quality metal finishing (machining marks, scratches) and incorrect insulator and electrode shapes. Genuine plugs have crisper printing, specific metal finishes, correct electrode shapes, and a high-quality terminal cap that won’t loosen by hand, while fakes often show signs of sloppy manufacturing and low-quality materials.

Packaging and box

  • Logo and text: Authentic boxes have the correct EAC certification logo and crisply printed text with consistent spacing. Fakes often have blurry, incorrect spacing, or are missing the NGK website.
  • Printing quality: Compare the printing on the box to a genuine one; fakes may have variations in the text or font.
  • Part number: The part number on the box may have different ink density (lighter or darker) or be printed in a slightly different location on fake plugs.

Spark plug body and components

  • Hexagon area: Look for a batch code stamped on the hex. Genuine plugs have a specific stamping style, while fakes may have a noticeably longer hex and machining score marks.
  • Ceramic insulator: Genuine plugs have a bright, clean white insulator. Fakes may have trapped air bubbles, a yellowish tint, a dirtier appearance, or less sharp printing on the body.
  • Metal shell: Fakes often have a shinier, less consistent finish with more visible machining marks, especially around the crimping and C-groove areas.
  • Terminal cap: Genuine caps are made of higher quality metal and will not loosen by hand; the dimple on the cap is centered and subtle. Fakes may have a lower-quality cap with visible casting lines, an off-center, deeper dimple, and can be finger-tightened.
  • Gasket/washer: Genuine plugs have a thinner washer with a tapered edge, while fakes may have a thicker, non-tapered washer.

Electrodes and tips

  • Iridium tip: Genuine iridium plugs have a small, precisely laser-welded iridium tip. Fake plugs are often missing this tip, or use a poorly welded, machined nickel substitute that is usually larger or smaller and less precise.
  • Electrode shape: Authentic ground electrodes have a consistent finish and rounded shape, with the correct gap to the center electrode. Fakes often have a messy, scratched finish, a more square shape, and the wrong gap.
  • Center electrode tip: The tip on genuine iridium plugs has a colored, burgundy hue, whereas fakes often lack this color difference.

Other indicators

  • Price: If the price seems too good to be true (e.g., a four-pack for a very low price), the plugs are almost certainly counterfeit.
  • Protective cap: The clear plastic tip protector on a genuine plug is longer and made of a harder plastic than the short, flimsy, and often ill-fitting one on a fake.

Here’s a link to a YouTube video explaining how to check some car plugs.

Testing NGK spark plugs