Aye Dave,
As SteveH says with the strip. If you have the bike on the sidestand you can take the cover off without loosing the oil. I found no wear in my plates and the springs little shortened, but had been using car grade 10-40W semi-synthetic oil.
Washed everything down with brake cleaner, re-assembled with original plates, new springs, new 'original equipment' Yamaha gasket (having had a pattern one blow, putting oil all over the back wheel at 60mph+ through some bends!

) and used 10-40W Halfrauds semi-synthetic motorcycle oil.
No more slipping and no sign of wear increase or problems with the engine to-date, 12K miles ago.
Hope this helps.
Regards, Bill.