Hi Wonga, and welcome to Outdoorking. There is a lot of good sense in what you've said. In the case of aussie's Greenfield, it has the later type of clutch linkage that is not adjustable (I was following the same line of thinking as you were until I found that out).
The Greenfield mowers use a system of forward and reverse clutches rather than a slipping belt system as most other mowers do. This means they can last a lot longer without new parts, but it is necessary to understand how they work, and repairs are more time-consuming when the clutches finally wear out.
We haven't completely worked out all that is happening to aussie's mower, but I currently have a theory that I haven't explained because we haven't yet clarified the current status of the machine. Posting "solutions" before you have the symptoms and circumstances clear is untidy (though it often works, and fairly often actually saves time). Yes, I know, I'm a victim of my own training as an engineer: it's warped my thinking. Freud would have said I'm suffering from a type of anal retentiveness.
