I imagine a bearing would probably rattle up even more and begin to knock as rpm increases, but could be wrong.
What have you done to try and isolate the cause?
Apply pressure to the pipe in different ways to see if it changes.
Remove the bash plate.
Check the carb, frame, plastics etc to see if it's something making contact. Rad shrouds can vibe against things sometimes and cause strange noises too.
Remove RHS PV cover, refit the pipe and check if the sound occurs at a given PV position. Check tension on the plate. Consider removing RHS cover and checking for contact against the cases from the linkages.
If you do that, check the mains on that side for play.
Remove flywheel cover and check that side as well.
You'll have to do some digging probably, but start with the easy ones and go from there.
