Just putting this out there. You say you've only had a very short time? Was the original owner riding it when you bought it? Reason I ask is if it was recently put back together to sell. Maybe your oil lines were put on backwards and there's plenty in the tank but barely any in the motor. Seen it happen to a friend out west, after he had put his bike back together he took his oil lines off the fitting and put them back on wrong...Oops.