Which engine do you have? I'm assuming a K series, but which one exactly? I think the note you are referring to in the manual actually has a typo in it, it is supposed to read any gas fueled engine that operates below 2500 RPM should have a plug gap of .018. There is an antique engine forum that has this note on their Kohler engine page that tells you what spark plug to use and what gap to have, but I have not read this forums rules on linking to other forums...so i won't link to it.
As far as setting the points gap goes, There is a "Static Timing Method" in section 8 of the K series manual that will tell you how to set the gap, or you can use this really good how to, that I have known many people to use successfully:
http://mgonitzke.net16.net/tools/static_timing.pdf
-Dusty
As far as setting the points gap goes, There is a "Static Timing Method" in section 8 of the K series manual that will tell you how to set the gap, or you can use this really good how to, that I have known many people to use successfully:
http://mgonitzke.net16.net/tools/static_timing.pdf
-Dusty