Pictures would really help. I am not an expert, but I have messed around with a few 5hp briggs, and from what I have seen, the engine side cover must come off buy sliding the cover over the crank shaft pto.
After the side cover is off, then you can remove the crankshaft. Again, from what I have taken apart and seen for myself, I just don't see how the side cover could get onto the crankshaft and then the block, with a gear or sprocket mounted on the pto.
Here is an exploded diagram of the Briggs engine I know. In order to get to the piston, camshaft, crankshaft, etc., you must first take of the engine side cover. Sorry the image is kind of small.
Hope that helped,
Gilbert