Are these the original parts? If they are you may well have a friction problem. Use the best metal polish you can find and polish the key pins, front and center, polish the tops of the capstans and make sure the center pins are all free as they should be. If the hammers have been changed then you likely have hammer to heavy for that action. Either reduce the weight of the hammers or install lighter hammers. Up weight is measured by placing a likely weight on the key, pressing the key down to let-off and using your fist hit the action lightly to break the static friction of the action parts. If the hammer raises fast there is too little weight. If it does not raise at all the weight is too high. The hammer should rise slowly but steadily. When you measure the down weight you do the same except you will measure from rest to let-off, not past, with the hammer going up at the same rate as in down weight. )Down weight plus up weight) divided by two will give you balance weight which should be in the 35 to 40 range. (Down weight minus up weight) divided by two gives you the friction for that key. It should be in the 12 range in the bass to about 7 in the treble. Higher numbers indicate too much friction or a major action geometry problem which should be addressed before changing the key weight. If this action has wippen helper springs their tension can be increased slightly to help but there is a limit to how much they can help. Weights should not be pounded into the keys, they should be pressed in with a drill press or an arbor press. This helps prevent splitting. The lead weights with two holes in them we call "Jiffy Leads" which means 'fast leads' They are a bit on the heavy side and certainly will increase the inertia of the action which can cause the pianist problems. They can be screwed to the bottom of the keys with very tiny and short screws. I use much shorter screws than those that come with the weights. Place some weights on top of a few keys to see how they feel before committing to screwing them on. Up weight, down weight and friction have to be taken into account every step along the way. It is very unlikely this action was made heavy by the factory so look at the situation carefully before running off and making changes.
This PTG archive page provided courtesy of Moy Piano Service, LLC