From the JK Products Facebook PAGE:
"JK Products® has and continues to work hard to improve the quality of all our products. Regarding our Hawk motors, our primary focus has been on reducing variability, so the difference between the fastest and slowest motors is as small as possible. The extremely competitive racing results obtained with JK motors is demonstrating the success of this program.
There are three primary areas where we have improved the motors dramatically and here's the information on one of them. While we would like to share the others, doing so would lessen the advantages JK has over its competitors. We want to stress these are not product specification changes, simply process and tolerance improvements.
JK has introduced the first 100% robotically computer-balanced motors in the slot car industry. This allows us to balance all our motors to a much tighter tolerance than is possible with a human balancing/grinding process our mass production competitors still use. A video of the balancing process is shown below and works as follows:
1. The operator rests an armature on the balancer.
2. The arm gets spun up and measured for imbalance at both ends of the shaft at the same time.
3. The arm is robotically moved to the grinding station.
4. The arm is computer ground/drilled as needed.
5. The arm is robotically returned to the balance station and measured for imbalance again.
6. If the arm does not pass the tolerance check, it goes back to step #3.
7. If the arm passes the balance tolerance check, a green light flashes, an alarm is sounded, and the arm is removed and replaced with the next arm for balancing."
(You'll have to click the link, as JK's privacy settings at Vimeo prevent embedding the video here.)