On May 13th of this year, David Stanwood articulated an approach to key/action balancing on the Pianotech forum at myptg.org. If you go to the main page and enter the first words of his post in the search box, the thread will come up. "You can measure the precise effect of the key leads" is your search string. Include the quotation marks.
The thread (Key Leads) was started in 2012, but resurrected by another tech this spring, for whom David jumped in with a reply.
I have been using the Stanwood Touch Weight kit from Pianotek Supply for several years, and have found the instructions that come with it very helpful. They included recommendations for working with wippen assist springs. These latest posts by David made the whole process a little less fussy for me. David has no problem with wippen springs, though I don't remember them being discussed in this latest series of posts.
The key is to take the factors that influence the touch, i.e. key front weight, wippen weight, spring influence, action ratio, friction, and optimal weight of hammers for the particular instrument, and manage them for the desired result.
I just rebuilt the action on a 1965 Yamaha G2. The original hammers were very light compared to those in the Yamaha -supplied G2 replacement set that has been sitting on my shelf for years. Using Stanwood's protocols, I ended up refining the individual hammer weights, adding quite a bit of weight to the fronts of the keys (though ending up 3 grams below Stanwood's recommended front weight ceiling, so not an excessive amount), and normalizing the friction. In this case no wippen springs were involved. I have had a very positive response to the result from users.
I would encourage you to work through David's approach. With it, you can determine if the springs are, in fact, desirable, or if the results you are after are better achieved by adjusting other factors.
Last edited by Floyd G; 08/31/18 03:10 PM.