westwood gemini rotavator

Hi all, new here and new to gardening and wanting to understand more as a past time and something to admire my hard work. we have a quarter of acre of back garden and needs some real attention to make is presentable really. Never done much more than digging and cutting the lawn. My parents are too ill now to really manage any gardening work etc so.. as a pass time when the weather imlroves it would be a moral booster and improves the view if i did something about it. i need to know what type of soil i have to work with. What would be beneficial for it i.e a good rotovating and manure and reseed. As the grass isnt very healthy or green. I know very little only from what i have seen in the good life haha! I also have a westwood gemini rotavator that i saved from my later grandfathers garage. Hadnt been run or touched in 20 years at least. I did have it running last summer ( i like all things with an engine). Requiring only a few things a new single pole unipac stator unit, new plug cap and an oil change and fresh petrol. It ran! It did do some very good work and helped us no end. But it did begin to play up and now i need some advice, i have found a few places to get spares, but have no info on this machine at all. I know. Its a westwood gemini rotavator i believe its a suffolk punch engine ( had a look for the 75sg14 code on the engine but nothing found what i found was totally different. Didnt indicate its engine size either. It uses points ignition with single pole stator (unipac) it has a zenith 13 tca-2 carburettor. It has a valve chest but has 2 screws on the outter edging of the chest cover ( not a single bolt/screw in the centre of the cover). I have stripped the engine knowing it runs albeit failing to run well after a good spell. To completely refurbish the engine. When we had it running, it did produce a little bit of smoke on idle and went away on half throttle. Is this normal. Id like to know.. roughly how old the engine could be?. If i remember correct the cylinder head is bolted down with 8 bolts. Here is a link to what i have. If you would like photos please feel free to ask ). Many thanks in advance ) Rob