When I went to start the BX yesterday, the battery was dead. Battery is only a few months old, so WTH? Charged it up and got the yard mowed and some tree trimming done, but let it run the whole 3.5 hours just to be safe. When I parked it, the battery was dead again and had to use a long screwdriver to shut the engine off. Didn't feel ike working on a hot tractor, so I went down this morning to check it out. Battery was down to ~6 volts, so I put the charger back on it for about a half hour to get it at least part way charged. The belt was on the dynamo so I checked the voltage and it was ~12.6 volts. Started it up and the voltage was the same. So after I got to checking I found the harness unplugged from the regulator/rectifier box. Plugged it back in and started it up and now got over 13 volts at the battery, so everything is working correctly again. Just for good measure, I ran a tyrap around the connector so it can't come apart again.
While I had the hood open I pulled out the radiator screen and cleaned a little debris off it. When I looked down at the rear facing radiator core this is what I saw.
Got the air hose and a blow gun with a 2 foot long nozzle and blew it out from the front. She's clean as a whistle now.