Spark Plug reach-why not use longer?
I noticed that the original spark plug of Chinese manufacture that was in my 66cc engine, has about a 1/2" reach (threaded portion). I replaced this spark plug with a NGK B6HS as one that was recommended on this forum with a similar reach. I noticed as I inserted this spark plug into the head, that it appears to have about 3/4" of thread. A spark plug with this reach should put the spark flush with the bottom of the engine head. I tried such a plug, and it worked just fine. I checked to make sure that it did not hit the top of the pistion. I am using a NGK N-3, that same spark plug that I use in my 2-cycle Bultaco motorcycle. What are your thoughts in this matter? BMF