There are two individual circuits that are not connected
The cranking circuit and the ignition circuit
The cranking circuit is a power circuit, connecting the battery to some thing
The ignition circuit is a ground circuit and connects the magneto to ground which prevents it sparking .
Where the problem comes is often the same switch or even relays are used on both circuits.
To me if I was to take a guess I would plug for a loose seat switch.
On the solenoid there are 1 or 2 small wires at the base, they are the trigger wires
One will have battery voltage & the other will be ground and BOTH can be switched.
If there is only 1 wire then you are lucky, it has to be a power wire & the ground for the trigger is the chassis bolts.
It really helps if you can get your hands on a wiring diagram, I can not find one .
The cranking circuit usually goes battery > fuse > Key switch B > Keys switch S > PTO switch > parking brake switch > one or both lap bar switches > solenoid ,
So using a test lamp hooked onto the battery neg, you can make your way back from either the battery or the solenoid .
If the brake / lap bar switches have 4 pins then the circuit is flat to flat .
My on site tool box has 1/2 dozen short patch cables with a male spade on each end and I use these to bypass the switches at the wiring plugs , one at a time till the engine cranks .
If you star by bridging the B & S on the back of the key switch plug then all you have to do is wait for the engine to crank when you bypass a switch which of course will be the culprit.
It is a PIA to do as the switch plugs are all in hard to get to places .
Now if the solenoid has the ground trigger as well, check it for ground before you start.
If there is none then put a ground jumper in and then turn the key switch to see if you have a power or ground circuit problem.
If you have a switched ground then it will run the lap bars and the power will run through the PTO & Brake switches.
If you have a 4 terminal seat switch and a switched ground solenoid then the ground for the cranking circuit will also pass through the seat switch
That is the end of the cranking
These used to be simple circuits , then red neck morons who believe it is a sign of freedom from the domination of authority started to promote bypassing / removing all safety switches
Bigger brain dead morons followed them like the messiah and of course ended up getting hurt.
Because nothing can ever be our own stupid fault, the mower companies got sued so the wiring became tamper proof.
Down side is you now have to pay a fortune for a technician to spend hours tracing electrical faults or spend a month on crutches after kicking the mower too hard if you attempt to fix it yourself.
