I recently took a 2400 mile ride on my old 1988 Heritage that has 110,000 miles on it. I noticed that the valve noise was increasing as the miles went by, it became worse at half throttle and up. When I returned home I rebuilt the oil pump and replaced all 4 lifters. I also installed an oil gauge to monitor the engines actual oil pressure. I inspected the cam for wear due to the miles I ran while it clattered. I did keep the engine at lower speeds to reduce the danger of further damage.
After the repairs were completed on the old Evo, it is quiet at all rpms, and it's performance was greatly increased. The lifters were failing to pump up to there proper levels and thus lowing performance and creating excessive valve noise.
I also have time savers, so is you have these be sure to follow the installation instructions to the letter, and remember that the thread count determines the amount of flats required in adjustment.
wolfeman181