I know the 2v GS650 is the direct decedent of the 2v GS550, to the point that a 650 top end is a nice hop up for the 550.
The 4v 550 on the other hand I know little about and haven't had much luck determining if it shares a block setup with the other 4v mills from that era. I'm contemplating racing one and have a 682.5cc cap to work with, if later Katana 600 or GS650 blocks swap over that makes finding some more power an easy prospect.
The 4v 550 on the other hand I know little about and haven't had much luck determining if it shares a block setup with the other 4v mills from that era. I'm contemplating racing one and have a 682.5cc cap to work with, if later Katana 600 or GS650 blocks swap over that makes finding some more power an easy prospect.