OK, I finally figured out why Harley has that feature where you turn on the ignition and open the throttle to more than 50%, then the fans and the pump operate. This is used when filling and purging the air from the coolant system. It wasn't intended that the customer do this on a regular basis after a ride.
The system is supposed to automatically keep the pump and fans running for up to three minutes after you shut the engine down, depending on coolant temperature. If this part of the system isn't working, I could see where a one quart system could easily become over pressurized and blow coolant out the overflow. If it's a design issue, as opposed to a defect in production parts that wasn't in the preproduction parts used in "testing", then it makes no sense that Harley didn't find and fix this long before they shipped the first unit to a dealership. When I say it makes no sense, I mean that in terms of not making sense if in fact we were talking about a company that truly tests its products before releasing them to the public. Based on recent history Harley doesn't have much of a reputation for catching the screw-ups in preproduction testing, leading many of us to assume they don't really do much testing or they don't have a clue how to design tests that will expose those defects. Sad either way, and even sadder that they did it again on a relatively simple cooling system that they need to have the consumers embrace if they are to be able to continue selling their 110 year old design.
Jerry