Similar story...first time i rode a motorcycle was the time I bought a used one for $1400 at a guys house. Took off, immediately hopped a curb and rode across the neighbors grass lol.
Had NO idea what countersteering....figured it would be exactly like riding a bike. Not so much. With weights 10,20, 30, or 40 times that of a bike...unconciously countersteering doesnt cut it. You need to put some effort into it.
You notice the same effect on fast or sharp turns with a bicycle. You do have to put some real pressure on the inside bar to keep the bike leaning over.