Honda BF9.9A-BF15A Outboard Motors Shop Manual., Page 73Get this manual
HONDA BFS.BABF15A
VALVE GUIDE REAMING
For best results, be sure the cylinder head is room temperature before reaming valve guides1) Coat the reamer and valve guide with cutting oil
2) Rotate the reamer clockwise through the valve guide the full length of the reamer
3) Continue to rotate the reamer clockwise while removing
it from the valve guide
4) Thoroughly clean the cylinder head to remove any cutting residue