It is probably a lean seizure due to lack of fuel. Fix the cap before riding further. Sooner or later you'll kill it.
In reality there's no such thing as a partial seizure. If it sticks and stops running it's a seizure. There are varying degrees of damage from seizure. Pull the pipe and have a peek into the exhaust port to see the damage. Post up some photos if ya can.
If you're going to be crazy,you have to get paid for it or you'll get locked up.
Hunter S. Thompson