I had a small carb (not sohc) that is essentially a pilot jet system with no needle valve, just air passages to meter the fuel.
Been left atanding about ten years and I could not get through the small airways with anything physical and the jet holes are really small stopping it from running at all.
Wondering what to do with it, so bit of lateral thinking (deck-chair, sunny garden, cold beer) and came up with boiling it.
So 50p on a old saucpan at the local car boot, gentle simmer in plain water for 15mins.......and clean as a whistle, reassmbled, primed and motor fired second try.
Used to run a chemical analytical lab and remembered that they always used to steam all the kit to clean it of any residue, also they use steam in other industries like petro-chemical....so that's my thinking logic and it does seem to be effective for naff all cost.
Suppose you could also use one of those walpaper steam/stripper kits with a nozzle to clean out oilways, carbs etc.
Let us know if you try it with any success.
Nigel.