i did some research on this issue with exhaust fumes and honda said that a worn out fuel pressure regulator would cause the motor to run rich. some symptoms of a bad FPR is uneven idle, decreased performance, cooler exhaust temperatures, black smoke when reving. im gonna try replacing the fpr when i get the chance and hope this helps

 

The reason that you smell like exhaust after riding the CBR is likely due to a low pressure zone created behind you when riding. Because the exhaust is under the seat, exhaust is entering this low pressure zone, and swirling air currents will actually propagate some of this exhaust forward onto the rider. Because most other bikes don't have the tail exhaust, they don't have the issue to the same extent to which the CBR does.