212 Motor Grader

I tried to start diesel engine with pony motor after engaging starter pinion. The big motor turned approximately 1/4 turn and locked up slipping the clutch on my starter. So I took the plates off around the pinion latches and my son and I tried to disengage them with big screwdrivers. I hate to take the carter keys out and unscrew them if I don't have to because it used to kick out about right. I would appreciate any ideas on how to get the starter pinion disengaged from the starter ring of the big engine.
Thanks, Rick

well i think it could be done. hear a video that might help to see what's going on inside.
https://youtu.be/vo0m1XBqdBY

Thanks everybody for your helpful information and the video. I will attempt it again tomorrow.
Rick

Bear in mind the pinion is probably bound up if it stalled the pony. Try turning it backwards just a bit and the latch may disengage easier.