Spark Plug Caps - Spark Plugs - Resistor/Non Resistor

Author: Tri-Spark   Date Posted:22 February 2021 

We often get asked about spark plugs, spark plug caps and whether to use resistor or non-resistor.

You do need spark suppression with electronic ignition and we recommend either resistor type spark plugs or caps, not both, fitted to your engine.    Spark noise is like the electrical equivalent of a Tsunami or Tornado. The electrical noise interferes with all sorts of electronic items including the ignition and charging systems so adding spark suppression will reduce the noise and keep things running smoothly.  Keeps your GPS  happy too!

I use NGK B8ES spark plugs on my bikes, these are non-resistor spark plugs.  The resistor caps I use are NGK LB05EH as they are smaller I find they look more original and neater.   Other resistor caps I've used are NGK LB05EP and they are good too.

There is no harm in using iridium spark plugs like NGK BPR7EIX; we hear that people find some improvements to their bike. With these plugs we recommend non-resistor caps like NGK LZFH.  However, for the cost you might be better off to buy two sets of the standard type spark plugs to keep on hand for spares.

Your plug caps must be a good fit.   If your HT Leads and caps are old or poor quality you may find they expand with heat and fall off the plugs. The ones we recommend and sell are tight fitting and click positively onto the spark plug. The HT wire is simply cut to length and screwed into the socket for easy connection to the cap.

It's worth getting good quality high tension copper core spark plug leads suitable for motorbikes.  We don't recommend carbon core leads unless both moulded end fittings can be retained. Carbon leads are great for cars but not so good for bikes with high vibration and heat. Cutting carbon leads and fitting universal caps is generally not a good practice. Automotive leads are often odd colours and have unsightly printing down the length.  Our HT Leads have a stranded copper core inside two layers of very flexible silicone and rubber insulation perfect for motorbikes. 

In summary:

  • Use resistor spark plugs OR resistor caps, but not both
  • Resistor spark plug caps we recommend are NGK LB05EP or NGK LB05EH
  • Non resistor spark plug caps we recommend are NGK LZFH
  • Recommend HT copper core spark plug leads

Comments (1)

I'm not pedantic, not in the true sense of the wor

By: on 2 September 2023
Spark noise is more like the electrical equivalent of a Lightening Storm than a Tsunami or Tornado.

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