All 990s used to come std with a 17T front sprocket. Im not sure what year they started putting 16T on.
I use 17/45 on my bike most of the time but if im doing a softer ride with some bemmers then I will use 17/42 to give it a few more legs.
08 KTM 300 exce (small)
12 KTM 500 exc (medium)
07 KTM 990 Adv (large)