GC1720 has no electrical power at all

[Dmacleo]

That is why the question...

I find it odd the its start when "jumped" but not with its own battery.... Leads me to believe problem is either battery related or battery cable related if he is jumping at starter...

I suspect main power from tractor battery was used to bypass solenoid, simplest manner and no sep ground from another battery needed.
time will tell.
I am thinking its wire off solenoid that provides all dash power/solenoid/relay/key power and charging is bad or corroded,
and if I am wrong I will gladly own up to it LOL

 

[kenmbz]

Probably a fuse in line with the battery.....

 

[Dmacleo]

yeah could be there are 2 slow burns involved. also corrosion could be (although rare) enough so start circuit/dash don't work but the low pressure electric fuel pump (iirc from using my amphound (link) on it only uses on average 3 amps) may still work. pretty low draw. been a bit since I ran amphound on it though so maybe wrong.
if wasn't raining every day lately I'd run amphound just to refresh my memory.