I live in Myanmar and ride all over the place on my little 125 Chinese motorbike. I just got a newer Chinese dirtbike but it still just a 150cc. I did a trip when my dad came here that I blogged about. I have all the places we went on google maps so you can get an idea of where you can go. you can see my trip here www.myanmarmotorbiketrip2012.blogspot.com Some roads here are off limits or become off limits when incidents occur so it's good to watch the news and check out maps like these to get a general idea of where you can go.
Great blog and some good information with the extra link. Did you ever happen to notice if there were motorbike rentals in Yangon? Thanks
Sorry, There are no motorcycles allowed in Yangon. You can't even ride a bicycle there! Mandalay is the motorcycle capital of Myanmar so most rentals are out of here but you can rent bikes in some towns like Ngapali Beach, Kalaw, and Pyin Oo Lwin. I hear there are no places to rent in Bagan or Inle although they do have motorbikes on the road.