Spookytooth says the same thing
Blueprinting - Pull More Power From Your Engine
Probably the biggest and most helpful tip to ensure good longevity of their motorized bicycle is to be extremely easy on the engine upon initial start up and during break-in. The chrome liner of the cylinder needs cyclical heat tempering to get up to its optimal hardness. In order to accomplish this cyclical heat tempering, the bike should be kept at very low idle and ran for short amounts of time. We recommend a top speed of 15 mph for a 44T sprocket, and trips limited to 10 minutes. Follow this regimen for the first 3 tanks and the engine should develop 1/3rd more power and you will notice that all of the engine noises miraculously disappear.