I have noticed a whirring noise in the primary lately, I have about 13,500 miles in the clock.
Has anyone had to replace the shoe for the hydraulic adjuster in the primary?
Is it true you can use ATF in the primary?
Will it shift harsher?
Going too pull it apart this weekend but would like some input from an experienced member who has been there...

 

I just recently had to have mine serviced under warranty for a similar noise that got progressively louder. Turned out that the race on the main shaft had a huge section of metal that was pitted away! I could hear it more clearly after the primary fluid had warmed up and thinned out. The noise would present itself if I had the bike in neutral and let the clutch out. Then slowly disappear when I pulled the clutch in as the rotation of the clutch assembly stopped. Could be your culprit also....or it could very well be the primary chain tensioner.

And yes, you can use ATF in the primary. I actually prefer it because of the way the clutch engages vs. primary+ or 20w50 oil.

BTW, my mileage was approximately 14,000 when the noise had to be addressed. I got to see it myself and I'd have to say the reason for failure had to be a defect in the metal. It was only pitted in one section of the race. Not a rotating score or gouge as if something was eating at it while rotating.