Thanks everybody. Got a new spring for a princely sum of $3.50 which I thought was pretty good. Found where it goes from the parts diagram and now it purrs like a kitten. Plastic carbs are OK in my opinion after seeing so many chondas' with rusted out bowls. Thanks for the year built information. The mower doesn't look like it has done much work. Mackay is very patchy with its showers so if you're not lucky enough to be under the cloud dishing it out then you don't get any rain. I have seen it rain at my place but miss the street a 100 metres away! Cyclones are another matter. This mower may have been lucky in that regard. Most of the mowers I get from the recycle centre I sell for $85-$95 after the necessary repairs but this one is a little better.
Maybe I can screw a little more out of it....
Thanks all.