MIne is not an M8, it's a 2016 and I just had to have my lifters replaced right at 20,000 miles. Same issues, a louder than normal clatter at startup. My lifters were "frosted." Oddly enough MoCo warrantied the issue even though the service manual says frosted lifters do not affect their operation, so kudos to Harley this time. I used Amsoil, but I switched back to Mobile 1.
I've heard rumors that Harley says check the lifters every 20,000 miles, but that's not in the service or owner's manuals. If it turns out to be true, that's a a heck of a"tax" to pay for folks who ride 20,000 plus miles a year, especially when you add cam tensioners and the primary tensioner to it.
Last edited by PeteF; 09-18-2017 at 07:44 AM.