http://forum.motorcycle-usa.com/defa...?f=18&m=398516

Here’s is some good dialogue on the matter….

Backfiring is really a timing issue and the ignition being premature and backing firing through the carburetor. The other end is consider popping and is about unspent fuel igniting in the exhaust, the use of the term backfiring is or gets confused often. Backfiring through the carburetor or exhaust?