I have a 38" Bolens lawn tractor with a 15.5 B & S engine, which won't start. I have replaced and tested the battery, I have replaced the solenoid, I have replaced the ignition switch, but still no joy when I turn the key. The starter has been tested and it is working properly. I am now lost!!

How was the starter tested?

If you put jumper cables directly on the starter does the engine crank or not?

Beased on what you have said... I assume it's a no crank situation. Not a it spins but won't start.

The starter will turn the engine if you put power directly to it.