[Too Many Projects]

Couple things I see, 1 is the larger diameter knurl appears to be engaging the block, is it binding and causing the bolt to stop turning. 2. The end 3 threads appear to be packing dirt/oil/crap into the hole and may be stopping the bolt from turning. I "think" the outer starter hole is machine all the way thru and could be tapped further, if the threads stop short. I would run a tap into the block and see if it will clean out junk in a couple threads and allow the bolt to go in further. I would, also, test that larger knurl to see if it is causing a bind and file it down to fit. If all that comes out good, but the bolt still stops short, you can cut 3/8" off the bolt and still have plenty of thread to hold the starter.