Welcome to the forums. It could be the cable, but a lot of times on the Fourtrax 300 if the choke hasn't been used for a while, the choke piston valve seizes up down inside the carb. I would loosen the cable at the carb and try to pull the piston valve out. It should come out easily. If it doesn't, don't pull too hard on it or you will break the top of it off. Try spraying some penetrating oil down in the top of the piston valve and let it sit for a while. If it's not the piston valve stuck, then it's probably the cable seized up.