I'm going to have a go at making the inlet manifold flow a bit better on the 850 R that I'm currently rebuilding (basically I'm just faffing about cleaning up the intersection between the manifold and the head to avoid doing any REAL work !). Last time I did anything like this was years ago using rotary grinding stones but there must be a quicker, easier way to remove aluminium. Anyone recommend anything, are the cheap diamond rotary rasps on ebay any good, would rotary wood rasps be up to it ?