My Honda CB Unicorn is 96K running. I have changed cylinder block, ring piston, clutch plate 12K ago. Recently My bike not reving past 5K rpm. From 0 to 4K rpm it's quite fast and rev fast like before but after that when I rev nothing happened. I have inspect with a local technician and he told me to change carburetor but I am getting mileage 50 KM/ Liter so I am not convinced to change carburetor. My air Filter is also quite new(something 30 KM old). My choke cable also new. I also checked with another CDI unit but nothing changed.

Please guide me with a list of things I should check before replacing carburetor. I am still getting milage almost 50 and it's stock carburetor so I don't want to change carburetor.