I have a mtd yard machine that has a 18 hp brigs. This machine will only start and run buy shorting the 2 post on the solenoid, and the key on when you shut the key off it turns off.? The motor has been removed and put on another mower today and I have the same problem different solenoid, starting switch there are no safety switches on the new machine. I need to know what wires and in what position they go too on the starter switch.. it's getting dark please help...

Any possibility the other solenoid was in the same shape? Make sure all the wires are tight, as well as the battery cables to the battery, starter, etc. the key off and key on thing, pretty much doesn't mean much, except that any safetly switches seem to be working. http://www.tulsaenginewarehouse.com/drawings/allwiring.pdf
Maybe this will help