I own a 2012 yamaha sz-r. The bike was working perfectly till yesterday, i am a front in line rider, so i always revs to higher rpm while shifting. Yesterday i noticed that when i got over 5k rpm, the exhaust started making misfire noise, it was like a dull cracker sound. It only happens when i rev higher or at higher rpm. Please help me, i went to a mechanic and he said it isn't a big issue and its not a problem. Please suggest me a way to handle the issue