I would suspect the gearbox output ball/needle races.
Was at a main dealers recently and was called into the workshop to look at a 12R that they were fitting the 4th belt to.
'Technician' told me that he couldn't understand why a new belt would be so slack, I asked if the wheel bearings, idler bearings, swingarm bearings and gearbox bearings were OK, question was met with a blank expression.
Walked up to the bike and grabbed the front pulley = loadsa play......told the 'technician' to remove the plug seal, which he did, revealing totally trashed mainshaft outer needle bearing.He couldn't believe it and said he'd never seen anything like that before.....I went on to tell him that all 'sportster' units have done this forever
They couldn't believe the book time to replace the bearing versus their labour rate and managed to work out, all on their own, that the bike was a write off
.......and this was after they'd done a full service, fitted a new battery etc. which they still required the customer to pay for......even though the invoice stated that the bike should not be ridden until it's unsafe condition was attended to
