Are you saying the bracket that holds the rocker arm and pivot adjusting bolt has come loose. Not for sure how your engine is made but just did some work on a FS600V today. I was replacing the rocker arms, bolts, brackets and pushrods. On these if you remove the nut from the adjusting pivot bolt the bolt can be removed freeing the rocker arm from the bracket. I thought I had some wear causing some problems but the new stuff hasn't helped. The new rocker arm has been changed to a different design from the old one where it contacts the valve stem. You will need piston on TDC of compression stroke for adjusting valve clearance. My setting for my engine was .005. Turn engine until the left hand magnet on flywheel is over the right hand coil ear. If that's not right for the valves to be closed turn engine one complete turn back to where you were. Turn the bolt that turns the concentric bushing to adjust valve clearance and tighten the nut while holding the bolt.