Hack Method of refilling
Right or wrong, after I replaced my wife's 650 twin's radiator I too ran into the red triangle and found the fluid level low from not properly bleeding the system. I simply let the bike idle with the radiator cap off, while watching to make sure the bike was not overheating, and just filled the radiator a little at a time until it maintained a level near the neck of the fill area. Yes it burped out some fluid from time to time and got some drips here and there, but once I did that then filled the reservoir after placing the cap back on the radiator, it has been fine since. Simple, effective, and probably way wrong!!