Comparing the F658GS to the F800GS
The F658GS has less lift on the cams,
more conservative ignition timing (and burns regular gas),
does not need the "secondary air" system that is provisioned into the valve cover but unused on the F658GS
there may be other things also ....
A nice table of the F650GS / F700GS / F800GS / F800GT would be nice reading material .......
