I have a Yamaha XVS1100 that I bought new a few months ago. Twice now on starting her up she has backfired with flames coming out of the exhaust pipe. It was so loud that it made my ears ring for a few minutes afterwards. I guess what I want to know is: 1. Is this normal? 2. Is it harmful to my bike? 3. Is there anything that I am doing wrong that is making it do that? Thanks in advance.