About 5 years ago, I bought 19 of these mowers from a property maintenance company that went out of business. They were ok from the perspective of nice wheels, commercial tank, drive system but I wasn't really sold on the 4 cycle engine. Some of the machines were brand new and most of the others were only a season old. I found that some smoked severely (white / blue smoke from oil) on occasion upon start up and would not stop smoking until shut down. After shutting down, if immediately started, the smoke was gone... go figure??
Anyway, I used one for a complete season, sold the rest and went back to the 2 cycle LB's and probably would never go back to one. For home use great, but commercial use I still prefer the 2 strokes. Just my opinion and preference.
my quantums have all been smokers too. short on power too but all have run reliable. the quantum was a poor choice for toro to offer on this model as it was supposed to be for commercial work. the honda 190/160v or a kawi would have been a better choise and might have sold a lot better. they had trouble selling these as they sat on the dealers floor with no takers.