2005 Majesty 400 Slow acceleration

I just bought a 2005 Yamaha Majesty 400 that does run, but not fast at all. It is slow to accelerate and only reaches speeds between 40 to 50mph. Can anyone tell me what I should do to get it running right. I once had a 1987 Honda Elite 250 that was alot faster than this 400 I now own.