My nsr250sp mc21 has developed a flat spot at around 6-6.5k rpm. Any ideas what xoild be causing it? The bike is run regularly has done 20k kms and is completely standard.

When was the last time you used carb/injector cleaner in the tank?

Flat spots on 2Ts, is normally a fuel delivery issue.

I cleaned mine thoroughly, and even polished up all the rough edges. Runs smooth and starts on the first kick