Yahya Omarjee

Hi, I've recently purchased a 2 stroke 2007 Honda CR 250. The bike has been standing for 6 months. I topped up the coolant till just below the neck and replaced the radiator cap. As soon as I start the bike the coolant pours out of the overflow pipe, if I rev, more seems to empty out. Haven't driven the bike as I'm scared it might lead to bigger issues. Any idea what might be the problem or what I can do before I go a mechanic and pay through my teeth