You need to take off the entire right side cover, not just the clutch cover. It's not too much more of a hassle. Besides, you are going to have to hunt around for the broken rod. When you put the cover back on, put the right cover on with the clutch cover still open then make absolutely, positively , 110% sure both the advancer gear and the water pump gear are correctly engaged before you button it back up.
ps. a new advancer rod is $7 and change, but while you are in there, take apart the advancer centrifugal mechanism and inspect the pancake bearings & replace if needed (again around $7 per each). Also, remember that the nut holding the "claw" gear at the top of the shaft by the cylinder head KIPS mechanism is a LEFT HAND THREAD