You need to start by learning how an engine works, what a four stroke engine is, and learn some of the names of the basic parts and where they're at on an engine.
Then I would suggest downloading some Ducati manuals and start looking through them. Notice the differences between liquid cooled and air cooled engines, pushrod valve trains and desmodromic valve trains, and different types of final drive systems such as belts, chains or shaft drive.
Start with the Wiki topic of engines, then go to the download links for manuals. If you've got a specific question about something, hop back on Yahoo! Answers and post another question. Somebody out there knows the answer.
