There have been several versions of the 125, including both with and without electric start, one has a larger rear tire and a bit more power....
I don't remember exactly what model had what and what years they were available, but it seems like it was 2003 or 2004 when Yamaha started putting electric start on a lot of their trail bikes.
Check out
www.thumpertalk.com and see if some of the guys there know more. There is a TTR specific subforum.