I've been attempting to disassemble a generator at work to replace the starter cord. Being a suitcase-type generator, it's proved to be excessively painstaking. However, it's almost apart - I just have one bolt holding the remaining cover onto the generator. Unfortunately, I can't get the bolt undone.
The bolt is a fairly standard hex bolt, with the head on the outside of the generator. I can get a socket over the bolt just fine. My problem lies inside the generator with the nut, which is a square nut that's supposed to sit in a plastic holder to stop it from turning when you try to loosen the bolt. Annoyingly, the plastic holder is broken, so when I try to get the bolt out, it just results in the bolt and nut turning endlessly in the holder.
Being as the nut and holder are inside the generator, they're fairly difficult to get at - I've removed the side panel, so I have some access, but it's fairly limited. There's enough space to get a screwdriver in onto the top of the nut, but not much more - certainly not enough to get a socket or spanner or pliers onto the nut.
I should also note that this bolt will require significant torque to get started - it's been tightened by a power tool of some sort (no idea what); our rather limited selection of power tools don't have enough torque to do the job. It is possible to do by hand, with some effort - I've got the other bolts off - but this does mean that whether I'm trying to turn the bolt or keep the nut in place, it takes a lot of force.
A liberal application of WD40 hasn't helped; nor has any other combination of tools I've managed to come up with. What else can I do to get this bolt off?