i did this on my 250 while it was in car, in order to use a dampener installer tool instead of pounding in place and i did it using a regualat electric drill. it took me all of 10 mintes to drill and tap the hole. its easy to center because the groove on the crank pulley goes to a point in order to use a puller...you justcenter the drill bit on that and use pleanty of cutting oil.
