Starter solenoid troubles

[J-440]

Before I call Powermaster I need some expert advice. I recently bought a new starter and for some reason, the gear is not popping out all the way and engaging the flywheel. I've tried a longer spring, some washers, and even different lengths of screws to make the solenoid shaft longer with no luck. I've got 12.5 volts at the battery and have benched tested this thing several times. It spins fine with lots of torque but just doesn't pop out all the way. Do I need a longer solenoid? Thanks.