I have never done my own crank balancing; they have been done by a person who knows what he is doing.
But there are first times for everything……
Some time ago a neighbor had a look into the work shop; he had never been there before and where thrilled to see the “old” engines…..
Suddenly he said: “I think I have a tool you can find useful……..”
An old cast iron balancing tool.
I am overhauling a unit Triumph TR6 engine and wanted to check the balance factor of the crank. I did some reading of the subject, and got the weight of the rods, pistons, bolts and nuts. I bought some readymade weights from http://www.greeneysgarage.com/ . Put the crank in the tool……..But it was obviously not made for twin crank shafts……The adjuster wheels stopped the crank from turning…It`s probably better for single cranks…
But help is at hand……I borrowed a balancing jig from http://mechanicforlife.blogspot.com/
And the crank was spinning freely….And guess what, the crank was spot on to my requirements, no drilling was necessary!