I do not own a liquid cooled Harley, but, for 25 years I have used a 50/50 mix of distilled water and Prestone Extended Life (orange, silver jug) in everything I own that is liquid cooled on two and four wheels with absolutely zero issues. Way cheaper than HD/Honda/Kawasaki pre mix.
The two types of automotive coolant in wide use are the blue/green/yellow Ethylene glycol and the pink/almost any color you want Propylene glycol.
Ethylene glycol brakes down into a bunch of acidic compounds. Acetic, oxalic, glycolic, and glyoxalic acid being the ones that do the damage. And they tend to attack rtv and sme plastics, making them unsuitable for use in newer vehicles. There is also much more electrolytic action between dissimilar metals. And it tends to cause salt crystals to form over time, these abrade the seals in pumps and valves, as well as precipitating out on the surfaces of the radiator and heater cores.
Propylene glycol addresses the incompatibility with plastics because it breaks down into lactic acid. But it will still corrode metal. At least it changes color as it becomes acidic. But being non toxic, it is subject to being colonizes by organics, the slime you sometimes find in unmaintained systems.
With Ethylene glycol, the mix can be run as high as 70/30 to get additional protection. But as the Ethylene glycol content of the mix goes up, so does the corrosiveness. So thinning the mix made things like heater cores and freeze plugs last longer. 40/60 protected to -10 and was about 25% less corrosive than the common 50/50 mix. Down south a qt to the gallon of water was fine for the occasional frost. Funny thing about it is that pure Ethylene glycol protects the same as a 30/70 mix, but when heated will eat cast iron. Back in the day, how many people did you see drain the radiator in the fall and then fill it up with straight antifreeze? Or add straight antifreeze to their leaking systems. Wonder what mix they ended up with?
Propylene glycol does not freeze protect as well as Ethylene glycol, so 50/50 is about the same as 40/60 on the old stuff. It is very subject to reacting with some impurities in tap water. Iron and calcium being the most common. They will shorten the life considerably. So it is usually sold pre mixed. And these days its designer coolant. Just like with brake fluid, each manufacturer will add supplements to address their particular needs (engineering mistakes?).