Hi Joe, welcome to Outdoorking.
It is the engine that is a GXV160, you haven't told us what the mower is. If it is one of the specifically Australian models, it might be an HRU216, HRU196, or something odd such as a utility. Any HRU model is a specifically Australian effort, and I've never seen or heard of a workshop manual for any of them. Here is an owner manual for one of the international models of 21 inch self-propelled Hondas with the GXV160 engine:
http://dl.owneriq.net/9/9da3d438-eee3-47a6-b571-b9bdab4040f6.pdfPlease post some pictures of your mower, so we can try to identify it.
Post Edit: The mower is not a Honda, it is an unbranded machine that has a Honda engine.The first question you need to resolve, aside from what model your Honda is, is whether it is in a safe condition to start. That means checking whether the sump is full of oil, and whether that oil is reasonably clean. Having jumped that hurdle, the next step would be to prop up the back of the mower securely with the blades off the ground, and start the engine, following the instructions in the owner manual. See if the wheel drive can be engaged, and whether the rear axles rotate when you do so. If they do, you can begin to hope the previous owner's problem was with the over-running clutches on both rear wheels. If the axles do not rotate, you have a lot more to worry about than wheels and wheel-clutches, and we can get focused on the (rather complicated) Honda self-propulsion system.
