Hi Aiden,
Sadly this much mistreated machine has seen better days. That rear roller is paper thin and not worth repairing. I'd say most of the drive train toothed gears are well and truly worn out as well.
As far as the engine is concerned they never run well with out some sort of weight attached to the PTO shaft. This engine is a much later produced power plant than the mower itself.
Honestly Aiden I'm not sure if this one is worth salvaging because it's going to come at the cost of another machine having to die to give any signs of life to this one. I'd also feel that this chassis will have a few more stress fractures underneath the paint in the engine deck rails than just one, which in that case makes it the heart donor to another.
Sorry to be the bearer of bad news but that's just how it is sometimes unless you have good engineering services at no cost available to you.
As you well know there's good cars and there are bad ones out there and this is the bad one that's been traded in.
Cheers,
BB.
