Hello everyone I had to replace the oil sump on my toro 22 recycler. I replaced the oil sump the pan gasket and the crankshaft oil seal. I made sure the timing marks lined up reinstalled the governor and the oil sump goes on easy no problem. My problem is after I mount the engine back to the mower I can't pull the pull cord. I removed the spark plug still nothing. Any ideas of what might be causing this issue. I've removed and checked everything 3 times with the same outcome.

Can you spin it by using the blade?
 
If still stuck, your going to have to break it down again.
This time, monitoring, WHEN exactly(in the progress) it locks up.
 
I would also spin it slowly while upside down before you put the cover on-
to  make sure the cam is fully in, nothing protruding out.
 
.
 
uding