I use to wheelie for quite a while. Had about a mile before i would get tired. Got out of the whole stunt thing though.
Just remember, cover that rear brake and take it slow. You start trying to force wheelies by throttling them out, and you risk the rear tire walking (wobbling) which could be bad at a 70 mph stand up. Especially if you end up putting it down crooked.
Cakes misses the days of my highway wheelie antics....
