Todwic, since you have just "handled your crank" you will remember how blunt it is.

The counter weights that is.

Now think about those blunt edges swinging around at 6,000 RPM and all the air it has to push aside. Make them sharp and though they have to push aside the air it's far less of a drag. The following or trailing edge is sharpened too.

Since you have removed a considerable amount of weight off of the crank you can remove the counter balance shafts and recover the bit of horse power it takes to spin them besides take them along for the ride.