What is the difference between a 2 cycle spark plug and a 4 cycle spark plug?

Question

I ask the question because certain plugs are designated for 2 cycle use as opposed to 4 cycle use. I know that if one uses a 4 cycle plug in a 2 cycle engine it will foul out more quickly than if you use the correct plug.

Answer 1

each spark plug manufacturer has a hundred or so different part #'s for plugs and the design differs slightly on each one from the extension of the electrode to the heat range to the reach into the cylinder. you need to access the catalog of your respective mfg. and look up the correct part # for your application. On AC Delco, Champion, NGK, Motorcraft ( some that I have dealt with) each letter and number of the part number is descriptive of one of the characteristics of the plug.
Delco R45TS -
R - resistor plug for use in vehicles with radio reception
45 - heat range
T - 5/8" plug
S - Extended electrode gapped at .045
Make it an R45TSX and the gap chahges to .060
R45SX - is a 13/16 plug (missing T) gapped at .060
I wasn't involved with a lot of bikes and marine apps but a parts guy there should be able to give you the same read if you want to adjust heat range or something in your app.

Answer 2

There is no difference in the plugs, the difference is in the basic engine design

Answer 3

one has a gas-oil mixture, the other is just gas