[OutToWinPAHC]

Depends on displacement, compression, cam, but most evo's and shovels run 30-35 BTDC. The sound is actually from the engine design.

"the crankshaft has only one pin, and both piston rods connect to it. This design, combined with the V arrangement of the cylinders, means that the pistons cannot fire at even intervals. Instead of one piston firing every 360 degrees, a Harley engine goes like this:

* A piston fires.
* The next piston fires at 315 degrees.
* There is a 405-degree gap.
* A piston fires.
* The next piston fires at 315 degrees.
* There is a 405-degree gap.

 

[OutToWinPAHC]

Yea they are conventional much like a car, and fire every 180 degrees apart.