Re clutch slip ...
if in doubt about an oil's suitability for a wet clutch, look for the 2-letter additive code, which starts 'S' ... and you want nothing 'later' than 'SG' as everything after this has friction-reducers (for car engines mostly) which screw up a wet clutch.
You will find all bike oils which say they are suitable for wet clutches have this code.
In my experience if you have run a clutch in a non-SG oil, the plates will need replacing as they will look really nice, but wont grip properly :-)
Oh - and clutch springs - some of us dd-boys have uprated springs even in our humble 600's ...
my 620 has 996 clutch springs plus an additional (steel) plate
I will be checking the 583 clutch and comparing the two shortly
[Edited on 28-12-2005 by phil_h]