My 110 has always been very noise between 2600-3100 revs. Had the dealership look at it and say they wouldn't worry about and just ride it. Well that little piece of advise has finally bit me. Coming back from Sturgis I could tell something wasn't right. The bike got me home but when I got there I stuck a borescope down the cylinders and both pistons have heavy pitting. The bike has always had good oil pressure and ran well besides the noise. Now the bike has extended warranty but I am guessing they are going to blame it on my exhaust and tune causing the issue. But I have a hard time believing that since it is running richer than when it came from the factory. I know bad gas could/will cause this but that would of been a lot of bad gas and I haven't experienced any of that. Just hope the heads will be salvageable and only the pistons will need to replaced.
The noise most times will come from the spring pressure in the heads being heavier than is needed, less than great lifters and last but not least the 255 cam ( stock ) is a aggressive cam lobe profile wise.. Now I have had customers that want to keep the cam as is, a simple valve spring swap will reduce 95% of the noise provided the lifters are still in decent shape. .
Now that it is under the new warranty find a shop that build and tunes in house and let the sort it out for you.. Does no longer have to be a HD dealer. Common service job for us. Springs lifters and customer is happy as the noise is gone.. Many of the owners are very happy with the power they have so cam wise if not damaged simple quick repair.
So parts list ( basic repair)
600 lift beehive springs ( avv my choice ) + seals
quality lifters ( many to choose from far from one company ruling there)
Maybe a tune if you are seeing some issue or at least check it.. Another reason to locate a shop that has a current up to date dyno.
Good luck