In all honesty with equally skilled riders the 490 was faster than the 501. It took a body builder to herd the 501 fast. The 125 MAICO had 21.5 hp at 8,200 rpm with a perfectly flat torque, "curve" from 4,000 to 8,200. It was a near verticle rise at the beginning and dropped like a cliff at the end. I can only guess that the rotary disc valve was responsible for the flat midrange.
I am going to run one of the C&H equipped engines today, it's 40- F out this am and really humid. About half raining.