Recently got a bobcat 743 on trade and its my first one. the guy said the motor runs and tilt and lift cylinders work fine. bobcat is a barn find and has been sitting for around 1 year. after I got it back to my shop I did the basics.. drained the fuel, coolant, removed the valve cover to check things out, changed the alt. belt and had the alt tested. I also removed and changed out the glow plugs (4). after refilling all the fluids and re primed the fuel system I went to start the motor for the first time. I cycled the plugs several times and it cranked over. Once I knew there was compression I went to start it again. After about four cranks the bobcat lunged forward and I heard a grinding of gears sound. I made sure it was in neutral and tried it again with the same result. not to sure where to start. from my understanding its chain driven.. could that be my problem? any pointers would be great.