The three wires on a M18 are a oil pressure switch wire that would go to the dash lamp "sentry", one from the voltage rectifier, and one that is the kill wire to the magneto.

Your kill relay circut is good, I'm running the same setup except using a toggle switch for 12v on pin 85 and my kill wire connected to 87a, (six or one half dozen to the other) it has worked flawlessly.

In regards to the pulley though, with a larger pulley on the engine you'll overspeed the charge pump which will create more heat and damage, maybe even cook it. A small change from 4.5 - 5" is probably not a cause for concern but a +1.5" will be.

Unless there's something I'm not aware of with this particular setup but as far as I've always known, it's not a good idea to speed up a hydraulic pump/motor faster than it was designed for. I am new to the world of Cub Cadets though so someone please set me strait if I'm out of line here! Lol

I have an update on the wiring, the engine starts, charges and shuts off without the need of grounding the white wire? I currently don’t have the white wire from the m18 hooked to anything.

As far as the pulley, I do not understand the feedback. Since it is a PTO pulley I was assuming it would only impact the speed of the mower deck/snow blower when turned on?

My mistake, I was assuming there was a charge pump running off the pto.

No worries, I appreciate the feedback.

Just a thought, could the engine be shutting off with the key and no white wire attached due to the fuel solenoid? I am confused why it’s working properly without the white wire. I rather be right than lucky.

I have a late M-18's with a walbro carb, and it does have a shut off sol. but your engine would not run unless you have a power wire to that sol.
I was told by the previous owner of that motor was out of a cub.
What i don't know, is what cub it is out of, and what the carb is off of.
He said it was out of a 782 but that don't mean it was born with it. :bigthink:
I will say it runs sweet with that bad reputation walbro carb. :beerchug:

I see two wires going to the carb. One seems to be a ground and the other is super thin. I assumed it was some type of solenoid. Picture attached but is turned 90 degrees counter clockwise for some reason.

Dat sho' looks like a walley bugger car du later wif a fuel shut off solenoid.
Dat wood 'splain the stoppin without a kill wire. :biggrin2: :beerchug:
I would still use a either a relay or an ign switch to stop the engine instead of a fuel sol.

I had that problem on another forum, even rotating the photo before uploading didn't work but I figured out a work around on my own and it's always worked...crop the photo before uploading, even just a tiny sliver has always done the trick for me!

I hope that helps!