When was the last time you had your rocker arm assembly out for a good clean?
1. The hole in the top of each rocker arm should be cleaned/cleared (an appropriate diameter piece of wire works quite well).
2. The two rocket arm tubes should "ream-cleaned" down the center from end-to end; and, the oil "feed" holes should be cleaned cleared.
Regarding getting good settings for rocker arm gap settings:
3. When you have the rocker arm assembly out, take the assembly apart (keeping the parts in order) and look at the "contact surfaces" - if any surface is worn/cupped, grind it flat (I use a fine-grit belt sander).
