usually when a seller sells an engine, carburetor setting was tuned with his last run. and i think, its a good starting point already.
u have the chance, strip that engine, pay attention especially on bearings, scratches on the back plate, pit markings on the piston and button head. this marks tells its history.
Serpent S411 TE : ready to race
Tamiya TA05 VDF : sleeping mode
Align 450 sports v2 : tick-tock in progress