Sparkplug (spark plug) cross reference guide for Happy Time style engines

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.

Now you can go out and play till your hearts content.


Fabian

I was wondering in your opinion what heat range should be run in a given ambient temperature. I read somewhere to use the NGK BP5HS when the outside temp is below 70F and the NGK BP6HS from 70F to 110F. I found the ACDelco R44F which should be the equivalent to the BP5HS(according to CarQuest) and tried it out in temps under 70F and it ran ok but best at temps below 60F. The NGK B6HS tends to run well at all temps even warmer temps up to 96F this week in SoCal but always feels less powerful than the hotter range ACDELCO R44F. Maybe just between nice cold air in the cylinder and a nice hot plug its the best combo... And its hard to compare across different manufacturers so i was wondering if anyone else has figured this out.
Also tried a plug a local mechanic with a MB recommended that he found at a local mower shop. Oregon 77-301-1 plug is much shorter than the others but is the same length into the cylinder. The cross references on the box are to NGK B2LM Champion J19LM and the Bosch W9E0. He swears by this plug even after trying loaning him my B6HS to try out.
For now my NGK B6HS is staying in til i can figure out the best iridium plug to go with and probably shell out the $7-$8 for one rather than the $2.50 i've spent each of the ones i've bought so far. So if you know the best one that iridium plug out there let me know.
 
Make your own spark plug testor, $3 (yes three dollars)

http://www.kartingtechinfo.com/tech/SPARKTST.JPG
SPARKTST.JPG


Basically it holds and grounds the plug while you "start" the motor and see with your own engine and ignition system what the spark looks like, or if plug is dead. Be cautious, as obviously an open spark can ignite fuel vapors!
 
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