I ended up buying a 1995 Commodore B14 yesterday -- not exactly old but a lovely, lovely example. It is in fantastic condition and came with the original receipt and service papers from the chap's father. There's no rust on it and everything has cleaned up very well. It was sold as not starting and "requiring tuning". It has been stored dry in a ventilated garage for 2 years.
I got it home and took a look at things. To begin with the gasket between the air filter housing and the carburettor was hanging only on one screw and when opening the carb up (as best I could on these modern carbs) there was debris inside. The rubber float bowl seal was broken too. I let it soak in carb cleaner overnight and it looked new when I took it out this evening. I sprayed cleaner and air through it after and let it dry. I did refit everything even with the broken float bowl seal while I await a new one.
It started on the second pull but only runs with the choke fully open (or ON). It is a little rough idling but doesn't cut out.
I think these mowers use a Tillotson carb? The one I have is identical to the picture below. I'm not familar with these carbs. A clear problem with it is that when opening up the screw at the bottom even very slightly, it pours petrol out of a small hole on the bottom. What could the problem be here? I'm not even sure how to prime/tickle the carb.
PS -- thanks to wristpin on my earlier "Scarifier or Aerator" thread. I am on the lookout for the grass rake springs online.