Big Coolant Leak while STOPPED

I had the strangest issue with my bike last Sunday. For about two weeks or so I could smell anti-freeze/coolant but could not see any leaks or signs of a leak. So Sunday while up in the mountains, when I stopped at a rest area and turned-off the engine, coolant would build-up in the expansion tank and over-flow which left a small puddle of coolant on the ground. It happened twice. A few minutes later when the bike cooled it would suck-up all the coolant that was left in the expansion tank until it was empty. A Japanese friend I was riding with called Marutomi KTM shop in Yokohama and they immediately knew what the problem was. I needed a “new radiator cap” of all things. Lucky for me they had one in stock so my day of riding was cut a little short. First time I have ever had a radiator cap go bad! Anyone else have a similar problem

yep! quite a few people have!

My SD was fine until I gave it a overhaul, including all new radiator fluid. It was only then that she did the same thing.

But like you, easy fix. New radiator cap and it's all good

Now that I read this I believe the same thing has happened to my SMT this spring. For no apparant reason a puddle formed under it after letting it warm up enough for the fan to come on. I asked around a bit but no one could provide an answer. So it might be my cap, the problem has since stopped.