wow thats compleatly the opposite from my experience...Yamalube is ok, but there ARE better oils, amsoil, MC1, even Castor is better than yamalube in a high rev engine...
From what I have sceen non-synthetics seem to seperate more, and leave more deposits, namely castor...After I mix MC1 (full synthetic) it seems to stay pretty mixed in, of course I always mix the gas and oil up before riding anyways..SDD's pistons were WAY cleaner from running MC1 for 5 years than mine were from running yamalube for 4, and also much cleaner than before I switched off castor after a couple rides....
Yamalube is ok though I use it for break-in oil but I doubt I will use it everyday in the future.