Recently I've returned to the hobby after a long hiatus. Several of my Lionel o27 5121/5122 switches--from my original childhood set & two recently purchased used--had difficulty switching, especially from straight to turned-out, at below 50% throttle (Williams transformer). After some investigation, with all three switches, I discovered that the plunger was encountering resistance caused by irregularities of the inner plastic lining of the solenoid.
The solution: I picked up a the largest diameter round file that my local hardware store stocked, designed for sharpening chainsaw teeth, and carefully filed away the offending irregularities. Now all of my switches operate with ease.
I suspect that this is a common problem due to poor quality control, as two of the four switches from my original set & two of the four that I've recently purchased used all had this same flaw. Hopefully others will benefit from knowing of this simple repair.
