mm wrote:
It seems to me that all the screws and bolts on my Japanese motorcycle
are metric, except the sparkplugs.

AFAICT, neither the threads nor the socket required for the sparkplugs
used in my Honda are metric. Is that so, and how did it happen?


Huh? I though ALL sparkplugs were metric - a residual from the days (~1900)
when the ONLY sparkplugs a U.S. engine maker could get came from Europe.

Are you saying we are slowly converting Asia to the Imperial System?