copied and pasted from my 2016 FLHTKSE owners manual
I can see HD saying those after market grips or speakers are the reason your lifters failed, so no warranty!
This limited warranty will not apply to any motorcycle.
1.Which has not been operated or maintained as specified in the owner's manual.
2.Which has been abused, neglected, misused, improperly stored, used "off the highway," or used for racing or competition of any kind.
3.Which is not manufactured to comply with the laws of the market in which it is registered.
4.Which has off-road or competition parts installed to enhance performance, a trailer hitch, or has other unapproved modifications (even if these modifications include genuine Harley-Davidson parts and accessories that are not approved for use on your motorcycle). These modifications may void all or parts of your new motorcycle limited warranty. See an authorized Harley-Davidson dealer for details.
5.Which has been subjected to an act of God, war, riot, insurrection, nuclear contamination, natural disasters, including, but not limited to, lightning, forest fires, dust storms, hail storms, ice storms, earthquakes, or floods, or other circumstances out of Harley-Davidson's control.
6.Which has been in an accident or collision or has been dropped or struck.