I have an odd ball issue as of late on my 1980 448. I was blowing snow and having zero issues and then all of a sudden the tractor seemed to be running strange. I throttled down and all seemed fine so I throttled back up and said yep something is wrong. I attempted to shut the key off but the tractor kept running. I finally choked it to stall it out and then tried a restart, nothing dead as a door nail. The main fuse was blown so naturally I tried a new one and it also blew. Time to investigate.
First I did some preliminary checks of the wiring no rub through in fact it's all brand new. Tested the coil, checked points, and everything checked out. So I moved on to the Stator and regulator. I unplugged the regulator and it fires right up and does not blow the fuse at this point. Check stator voltage and it was over 40 at wide open so that's all good. I plugged the regulator back in after cleaning it and it's grounds and as soon as the key was at run the fuse blew again. One thing I noticed was the regulator was hot to the touch at that point. So my theory is the regulator is bad but can't get it to not blow the fuse long enough to fire the machine up and check output voltage.