Correct Spark Plug Gap K321

[dsmith41]

My Wheel Horse has a Kohler K321 engine and I was looking online at info for changing the spark plug. The correct gaps listed are as follows:

Battery/Breakerless 0.035"
Magneto 0.025"
Gaseous Fuel Engines (Magneto/Battery Only) 0.018"

What the heck does all that mean? What's the correct gap?

 

[old1]

If it has battery ignition, like a car, with points and an external coil, or the newer electronic ignition, set the plug to .035
If it is magneto ignition, with external points and internal coil, set to .025
If it runs on propane (gaseous, NOT gasoline) set to .018