Loud whining noise from speedfight2 and sound of exhaust blowing?

hi, i have speedfight 2 which makes a really loud whining noise when hitting above around 20mph but then stops at when the bike is at walking pace, you can only really hear it when slowing down. The exhaust is also really really loud. Any ideas what this may be please?

I had the rollers and clutch changed last week and also the carb jetted.

dave
August 2011