Just bought a 1997 shadow vt1100 c2ace with 16700 km on the meter. Also a lot of vibration especially after driving for more than 1/2 hr @ 120+ km/h. Vibration caused headaches after driving. I removed the windscreen. This gave a lot of relief. The windscreen appears to transmit vibration through the frame to the buddy seat. Now after a few weeks vibration seems to increase again, especially at low rpm and low speed like 60 or 70 km/h. I tried driving with an extra foam cushion on the buddy seat. This also gives good relief. It appears that the foam in the buddy seat is worn out and does not damp vibration of the engine enough. Next step will be refurbishment of the buddy seat. Anyone can confirm this?