Hi.
The motor is known as a "stepper motor" and is driven by a series of voltage pulses or steps. The software in the system knows the position of the motor by applying a known number of voltage steps to the motor. In normal operation, the motor can "slip" i.e. the motor shaft position relative to the number of pulses can shift - hence the need to routinely re-calibrate.
This is done by applying enough steps to the motor to guarantee it will be in the end position, known as overdriving. The mechanism will mechanically stop the motor at the end of it's travel whilst voltage steps continue to be applied. This occurs at every 5th switch off of the engine.
Unfortunately, the torque of the motor eventually results in the mechanism breaking as a result of this calibration procedure. (Try holding the motor still during this process and you will see what I mean!)
The bump stop position is easy to set, just move the mechanism to the end of its travel by hand and set the stop in that position. My linkage is broken in the same way as yours but this fix has been fine for many months now and just works by taking the strain out of the system.
Someone on this forum took the idea and made a much better stop than mine (electronic engineers make rubbish mechanical designers!!), you should be able to find it if you do a search.
Hope this helps.
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