I believe they're the rebirthed tecuseh's posssibly italian made, i think. So being a 40 its a 4hp but is pretty much a TVS90 with different carby jetting to get it up to the alleged 4hp. Year of manufacture is around 2000 and like most tecumseh takes 630ml of oil.
Yes, they are a smooth running engine when the carby's are right and masport used them a fair bit on a model they called the "Stinger". So if Bruce cant help you out with a filter try an authorised masport dealer, failing that cut one out of a large sponge oil it up and away you go.
Good luck.
