I'm not an expert either, but from what I can see on the Ducati Website the engine has an "irregular firing order."
A little websearch through Google revealed this article:
http://www.motorcycledaily.com/19feb...technical.html "
CAN YOU EXPLAIN HOW THE TWINPULSE WORKS?
Although it has four pistons, the Twinpulse maintains the typical characteristics of a twin-cylinder engine. Unlike a conventional four-cylinder unit, which has four distinct combustions for each complete cycle – that is, two turns of the crankshaft – the Twinpulse only has two. This is obtained by simultaneous combustion in the two cylinders of the same bank. The effect, which we have called Twinpulse, cannot be obtained by a four-cylinder engine by simply changing the firing order; it is necessary to design the entire engine with this function in mind, because many internal organs, which are stressed in a different and more ‘traumatic’ way, must be built to the right size."
Same article has lots of good info on Desmosedici and Testastretta engines.
Phill
[Edited on 16-6-2004 by phillc]