Much of the vibration arises from the linkages. They're too thin and deformable and the bearing points are too loose. If they were properly machined rather than pressed construction they wouldn't vibrate so much.

Just out of curiosity, what is the function, if any, of the small cup-like structure on the inside edge of the flywheel rim? There also appears to be another hole near the hub on the spoke opposite the cup structure. Perhaps this flywheel is used in more than one model the company makes.