Engine sound is good & seems refine if you start the bike first time in a day. after that when its engine get heat or after 10-15 minute run, engine & exhaust sound turns like a very old bike engine sound. I brought this in knowledge yamaha engineer, they said its sound changes once catalytic converter starts working. if anyone feels like that with their bikes. please comment. so that I could be able to understand that it is only with my bike or with others do.