Ok, so in 1st, 2nd and 3rd gear my bike reaches 12k rpms smoothly but once I shift to 4th there is a hesitation and then it smoothes out until about 7-8k rpms then it bounces around 8k then 7k then 9k...even if it's at full throttle.

The bike maxes out at about 180km/hour.

4th-6th gear are all like this. Is this a tranny problem?

I know the carbs need to be cleaned soon, but is there something else that may be causing this??

Cheers