I was riding my 1981 CB 750 Honda coustom the other day. I pulled in to a gas station and the back tire locked up and skidded to a stop. I got it home and tried turning the engine several different ways to no avail. I took off the valve cover and started looking at things. My timing chain had broke. I pulled it out but the engine still won´t turn over it moves about a 1/4 turn. I was wondering if anyone had any insight on what my be keeping it from turning over or what may have happened? Thank you