Within reason, age is not a problem for Australian petrol as long as it does not contain ethanol. The usual reason for hard starting with Honda engines is that the speed control cable and the ultra-complex linkage on the side of the engine near the carburetor is not closing the choke properly. That is especially true if it will start with priming (even priming with an engine-ruining substance, in this case).
Just remove the air cleaner, put the speed control all the way into the choke position, and look to see if the choke is completely closed. If it is not, you need to adjust both the clamp at the bottom end of the speed control cable, and the adjustment nut at the top of the same cable, so that you get both full choke at one end of the movement, and operation of the kill switch at the other end of the movement. It is a simple adjustment, takes about 2 minutes if you haven't done it before, less if you have.
Some Honda engines have a screw adjustment on the complex linkage that sets how far the choke is allowed to close.
If all of that is not clear, post some pictures of your linkage and we can try to translate all of this to suit your relatively large Honda.
There is one other point worth knowing about cold-starting Hondas. If you want the engine to be easy to start, do not run the carburetor dry when you finish using the engine. If you do, it will probably take 3 or 4 pulls to suck fuel through the various carburetor passages and get it to start.
