I changed my dual fire to a single fire as advised by my nephew.
Is there an advantage or disadvantage in doing this?

My mechanic brother who has owned Harleys for years says this:

This only really makes a difference if you're looking for every little bit of power. Either works fine but whichever you have making it adjustable is more beneficial. More online if you search single fire vs dual fire. It really depends on your usage.

Think it burns unused fuel. Not sure it would help performance. Would like to see actual Dual Ignitions like Aircraft. 2 Plugs in each cylinder, with separate ignition, when you shut down 1 ignition, you will see an RPM drop, so Dual Ignitions DO Help. Never seen on a Car or Motorcycle, may be out there. Will have to Google myself.