Dot stutter occures when your key produces an extra half dot at times.
Some keys suffer from dot stutter more than others. On keys that have little or no dot stutter, you will find that the dot arm dosnt flop around on the damper wheel.  As the reason for dot stutter is the movement of dot arm as its being dampened.  When your dot arm flops around on the damper, it just stands to reason it could add an additional half dot at times.  & If you load up your dot arm with more weights in order to slow it down, you will notice dot stutter gets worse as the heavier dot arm causes the damper to move around more. 
The best way to prevent Dot Stutter is to lock the damper in position and place 3M double backed tape around the damper wheel.  A side effect of using the 3M tape is the key will then become almost silent as the 3m material absorbs all the dot arm motion.  Another side effect of the 3m material is you be able to use a narrower dot contact spacing for sending higher speed code.   

There are a number of ways to help prevent dot stutter:
A. Using a wider dot contact spacing
B. Increase the dot side coil return tension
C. Unscrew the right side stop screw further to allow the dot arm to contact the damper wheel more securely.  
D. Place 3M double backed tape (on edge) around the damper wheel. 
Using the 3m double backed tape fix provides the best defense against dot stutter.    

1. Use a wider dot contact spacing.  The wider the dot contact spacing, the less a problem you will have with dot stutter.
 
2. Sometimes increasing the dot coil return tension will help -- but not on all keys.  Each key can have different keying characteristics due to the wide variation in main spring stiffness. 
3. Another thing that can help is to allow the dot arm to hit the damper more securely.  You can accomplish this by backing off the right side stop screw until the dot rod just touches the damper, then back off the stop screw another quarter turn or more.   So that the dot rod hits the damper wheel more securely and dosnt allow it to flop around as much.   Using 3m double backed tape around the damper wheel helps even more -- as in the next step.
4. You can find ways to dampen the dot arm more effectively.  Such as placing 3m double backed tape around the damper wheel.  As long as the dot arm contacts the 3m tape instead of the metal damper wheel, the 3m tape will almost instantly dampen the movement of the dot arm.  I've found quite a few speed keys that could never be adjusted for decent code without using the 3M double backed tape fix. So today I use the 3M damping material on all the speed keys.  
The type of 3m double backed tape is the Scotch 3M #314 used as mounting tape to hold items to walls.  But any type of the 3m double backed tape would probably work just as well. 

1. First,the articulated damper arm needs to be locked in position using a rubber band, string, dental floss etc..  On this key I used dental floss.  The thin dental floss can slip under the damper post and become almost invisible. As shown in the below picture.
2.  After you lock the damper arm in position with dental floss, lock the damper wheel by tightening its center screw. Then place some 3m double backed tape onto the damper wheel so that the tape is slightly larger diameter than the metal wheel.  The side that contacts the dot arm can be cut flat so that more surface area contacts the dot arm. 
With the 3M double backed tape in place, all the damping will take place on the surface of the 3m tape.  The 3m double backed tape will almost instantly dampen the dot arm. Thus preventing dot stutter.   It will also reduce the amount of noise the key makes.  A worthwhile advantage to using the 3M material on the damper wheel, is you can then unscrew the right stop screw further in order to allow the dot arm to contact the 3m material more securely.  Which helps to prevent dot stutter by not allowing the dot arm any chance to flop around on the 3m material. 

Once the 3M material is placed around the damper wheel, you will then be able to use a much narrower spacing for the dot contact.  And that will allow using the key with a lighter touch.  And a lighter touch allows for producing higher quality high speed code. So the 3M tape fix has a lot advantages.  You can easily remove the 3m tape later if desired.  And a person could even paint the white 3m material with silver paint to match the nickel plated piece parts.