I'm sure I don't know the fine points of spark gap, but I do have a
little experience.  In my college days my Vespa was my only ride and as
broke as I was a new sparkplug was a major expense.  I spent a lot of
time cleaning and adjusting the one spark plug on that two stroke motor.
As the spark plug wore out, the gap increased and starting became too
difficult.  If I set the gap too narrow it would fill up with carbon and
short out, but would be easy to start.  On the VWs I just set according
to specifications and forget about it...then change them maybe every
5000 miles or so...Whether they need it or not.

John Jensen, Mudbug Pottery
mudbug@toadhouse.com , http://www.toadhouse.com