Suzuki M120 2 stroke engine on Etesia PST?

I'm having problems with my Suzuki , it starts fine but will only run with a bit of choke , and without it's hunting. No it's not dirty jets , iv'e blown through all the jets with the air line , have tried 3 carbs. all cleaned beforehand , have tried 3 tanks, still exactly the same. Only thing I can think of is crank seals.
Has anybody come across this ?.
Would welcome any suggestions.