I was riding home on my 09 Heritage softail. At 75 mph on interstate it started making a noise that sounded like a broken rod. I pulled in the clutch and shut off engine and costed to the side of the road. Checked everything I could and found nothing unusual. I started engine and it was fine. I started riding it slow and when I got to 30mph it started making that noise again but not too bad cause I was driving slow. At 20 mph it didn"t make any noise so I drove it home that way. I removed primary case cover to check out things. Is what I found was a very loose primary chain. The automatic chain tensioner had stuck down and wouldn"t take up the slack in chain. I moved it up and down a few times and it got to where it would hold the tension. I adjusted clutch, cause it needed it, and put it all back together. I've put 500 miles on it with no more problems. I am going to get a new tensioner and put it on as soon as I can. So far all is well. Has anyone ever heard of this happening before?