So I have a fairly rough original Black Knight machine bought a few years ago that originally had plenty of issues, many of which I have managed to resolve. I had pretty weak flippers and replaced the mechanical portion (piston/lever arm/spring) of both lower playfield flippers with a newer and more reliable style (the type with the long, narrow tension spring holding the flipper in it's rest position rather than the large conical compression spring). The left side now works fine, but the right side is pathetic. It activates but very weakly, buzzing and struggling all the way. Here's what I can tell you:
The mechanism moves freely when I manually cycle it from beneath the table with no binding or unusual resistance compared to the good flipper on the other side
Voltage is about 37 volts at the leaf switch (I have cleaned with paper and get a good spark when I slowly close the switch wit the flipper button)
When I have the playfield tilted up on the prop rod, the flipper seems to be as quick and snappy as it should be, but as soon as I lower the playfield down again it is once again hopelessly weak. To me it seems like this must be some kind of mechanical binding, but honestly I can't feel any unusual resistance when I cycle it manually. Any suggestions on what I should check next?