I had that same seal leak on an 07 s2r 1K, almost same engine; (100 more cc's; and probably some more horses too
); I needed the valves serviced and before that belts replaced; the mechanic said it was a 10 minute job after the belts and covers are off; so let him do it all; cost more - but piece of mind.
you will need special castle nut tool
and torques (and locktight? )
belts back on correctly etc;
may be better to pay the expert mechanic, with so many items to do spacificly well ... and as per speeddogs cautions ...
Post and let us know how it goes; I'm home mechanically inclined; and have found sometimes it just ain't worth the worry.
That’s what I did. The mech did the seal change as part of the belt change. No point double dipping in the labour charge.
I guess if the leak was really bad you might. Mine was pretty bad, but I managed to hold off until the belt change.
I went a new castle nut too.