Honda GCV160 Lawn mower blade adapter removal

[henders]

I have a Honda GCV 160 lawnmower and their is a bolt in the blade adapter (it is cylinder not oval). I have taken the blades off but how do I loosen the bolt for the blade adapter? The flywheel and belt move anytime I try to loosen. It is one round cylinder. I can not locate anything to jam/stop that moving so I can take off the blade adapter. There was a small wire spring in lawn that I did not see and now wrapped around blade adapter underneath the housing.

 

[Rivets]

Try this, you will need the following. Pencil at least 6”, 18” cotton rope, long is OK, spark plug socket and wrench. Remove spark plug and insert pen and find BDC piston all the way down. Remove pencil and insert as much of the rope as you can. Rotate crankshaft in the direction you will need to loosen the bolt, until rope stops piston movement. At this point you should be able to break the bolt loose and remove it.