This is a repost of mine from elsewhere.
Ok, been doing some research as to alternative plugs for the NGK BP*HS series that we seem to commonly use in our Happy Time or China Girl 2-stroke engines.
Cross reference part numbers and equivalents.
NGK BP5HS = Denso W16FP-U or Denso Iridium IWF 16 = Bosch W8B or W8BC or W8BP = Champion L92Y
NGK BP6HS = Denso W20FP-U or Denso Iridium IWF 20 = Bosch W7B or W7BC or W7BP = Champion L87Y
NGK BP7HS = Denso W22FP-U or Denso Iridium IWF 22 = Bosch W5B or W5BC or W5BP = Champion L64Y
NGK BP8HS = Denso W24FP-U or Denso Iridium IWF 24 = Bosch = None......................= Champion L61Y
Unfortunately, neither Denso or NGK manufacture a supplementary gap spark plug (multi pronged) to suit a 12.7mm thread reach.
With NGK, each heat range figure gives 70 degrees celcius (158 degrees fahrenheit) temperature differential at the firing tip, to the next heat range above or below the nominated sparkplug.
So, a BP7HS runs 70 degrees hotter than a BP8HS or 70 degrees cooler than a BP6HS sparkplug.
The "P" in the NGK code (BP6HS) refers to a projector nose spark plug.
The projector nose sparkplug moves the firing tip further away from the cylinder head wall and to a more central location in the combustion chamber space with piston at top dead centre.
Now you can go out and play till your hearts content.
Fabian