15t sprocket gives better mileage but this is not a good combination for cb125f as pick up is not good but engine sound do less noise with 15t sprocket
Cdi unit play major role for top speed i got 105 max speed with 8.5 rpm while with stock sprocket 14t bike speed max 105 with 9.5 rpm
Cdi has lock engine rpm in 5th gear while with 15t sprocket i achieve top speed 110 in 4th gear with max rpm 11
But when i press the 5th gear speed goes down to 105 with max rpm 8.5
So cdi has lock its power to achieve top speed in 5th gear now i will change cdi unit with old model cg cdi as khan bhai told in his thread