Kinda of a trick, more like a fix
On the re501 5l rotovap, heres the fix to the noisy motor. Its motor lash, from what usalabs tech support called it. It makes a horrible shaking/off balance vibration.
Fix
Remove 5l bf
Remove motor cover (3x small screws)
Carefully loosen 4x motor mount screws about 2-4mm max.
Wiggle motor back and fourth, gently.
Tighten those 4x motor mount screws
Turn on and see of it still vibrates or is back to normal.
This fixed mine.
I couldnt go over 72rpm last night, was vibrating way too much. Now smooth as can be.