It appears that you have a manual fuel injector control. Here is a photo from the manual, not exactly your model, but I think that it is for the same engine.
Injector:
Item 11 is your stop/run/rpm control
I would start by checking the battery connections, both at the battery and the negative cable where it connects to the frame.
Is the battery the post type or bolt on type?
If post type, make sure that the post is clean and also the inside of the clamp on both cables.
Then I would start...
Update on my Hart Electric rider mower.
For the first time, I had to clean out the bottom of the deck. Really jammed full.
While I had the front of the mower raised up to clean the deck, I decided that maybe some moving parts should be oiled. The owners manual does not have any required lube...
A battery’s condition can be monitored by checking the electrolyte’s specific gravity with an inexpensive D-I-Y battery hydrometer to determine the percentage of sulphuric acid it contains.
A fully charged cell at 80 degrees F would show a specific gravity of 1.265. If all six cells are fully...
Nope, I think you had diagnosed the problem correctly.
Hind sight is always 20/20. You should have replace the governor assy when you changed the camshaft gear.
Richard
With the power connector to the clutch coil disconnected, check the coil to ground resistance. It should be in the millions of ohms.
If it is shorted to ground, it will cause excessive current flow.
Richard
You can obtain the user manual from JD. The manual is to large to post here, but here is a link to the user manual. Pick one of the three last choices:
https://techpubs.deere.com/en-US/Search/Equipment?page=0&sug=true&st=model&kw=GT245&ln=English
This sentence does not make sense. Do you mean that you checked the PTO switch?
You should not be measuring voltage with the meter in the ohms position.
Do you have the owners manual?
There should be some trouble shooting guides in it.
Richard