Customers often don't understand why I put 50-100 miles on a new bike/engine before I sell it to them. The difference in power is the main reason as well as differences in ease of starting and overall engine operation on a new engine and one that is slightly broken in is noticeable.

One new engine recently, wouldn't go faster than 15mpg unless I was going down hill. It took dozens of repeated short trips at varying throttle settings to finally get those rings to seat. Its up to 21 mph after 18 miles and should top out at 25mph.