What size is the crank bolt? The older engines 11mm headbolt engines had a 17mm bolt, the newer 12mm head bike engines have a 19mm 12pt bolt, maybe you have totally the wrong bolt, or your pulley is for older engine?
You should be able to get to the crank bolt with the pulleys on. That chain looks big enough to lift the engine, ha.
I think you need to replace that bolt with something that is longer and has a head on it that you can turn by hand with a wrench. I have an 81 with a 17mm head on it.