I own all Saitos. YS is a top of the line product and if it is new, there should be an instruction sheet that comes with the engine. My Saitos had fuel parameters, mainly oil @ 20%. Product directions are your BEST source of information..... not ME, or "most" anyone else. If the written directions are not clear enough, email or call the mfg./distributer. This is NOT a slam to others that may have suggestions. I am sure you gained your knowledge by running this engine over the years. But.....I have talked to many people in person, and here on the forums, about this "Saito 20% oil thing".
Half the guys say NO... I run... 16%-18% no problems, or no castor, 50% castor, on and on.....!! This is the point. YS is a very expensive engine. MOST guys know what they are doing. But if I were you, I would make sure you do as YS says. (for now), It just makes good sense to keep your warrany valid. After a while, you can "ease into" some other suggestions. .... lownslo....