I think that as long as you cover the whole surface to be painted would be enoght.. The primer is supposed to be a base for the other layers of paint to stick in, but I don't really know as I haven't painted anything like a bike frame before..
If you want to, I can ask to some friends, but I think that your question will be answered in a little while by someone with experience on that right here.. If not I'll tell you what I can find out..
2010 Honda XR 250 Tornado