On my '07 Street Bob, out for a spin the other day. After about 25 miles the motor was all warmed up and I'm hearing a loud tapping that seemed to be from the primary side, but was rpm related. Pulling in the clutch didn't change it. I changed the oil (syn) 2000 miles ago and keep on eye on the level weekly. There's 25K on the bike.
Cut my ride short, pulled the dipstick and was hit with a long blast of hot air. Lasted a few seconds. The oil level was barely on the bottom of the stick. The low oil light never came on, but it tests OK. No signs of any oil under or behind the motor.
I topped it up and took it out the next day. It ran fine, no noises all afternoon.
Just to be safe I changed the oil and took it out again. Still runs great. Both times when I got home I pulled the dipstick and there was no pressure.
So I'm wondering how the crankcase could get under some much pressure and then was fine after that. Would also be nice to know where the oil went.