Could be as Trailcutter said fan not working (so it boiled), or another issue some Vikings have is sand going up into the weep line on the water pump causing the mechanical seal to start losing coolant, and subsequently running low on coolant and overheating. Lucky you stopped and let it cool down, make sure that you bleed the coolant properly when you re-fill it, it's not just a matter of topping it up and riding again, there's a process to it, some winch the front of the Viking up in the air to help bleed, you can Google it. Hopefully your head gasket is ok, good luck!
Sent from the bottom of ANOTHER empty whiskey bottle.
Chookbanger Mark II,
Street legal Blue Viking, 2017 model, bought 3/4/2017.
Street legal Blue Viking, 2014 model bought 3/4/2014, sold 3/4/2017 with 2850 km and 189 Hrs.
Yamaha Saggy Bottom Club member.
Other Yamaha Bikes Currently Owned
2016 YZ85 (sold)
2017 Grizzly 350 4x2 Auto Quad
Honda 2012 CB250
Honda 1999 CT200
Honda 1985 CT200 Trike