This was one of those questions that got you thinking how little you know about the aircraft you fly so I got searching.
Found the following link which was of interest:-
http://www.lycoming.textron.com/main...ldWeather.html
Basically the article states that no two aircraft are necessarily the same and the number of cylinders that have priming lines is down to the manufacturer. I guess some of the old nags I have struggled to get started on a cold morning might have only had 1??