My little guy will be two on January 8th (Elvis' b-day, BTW) but he already knows how to twist the throttle, can turn and maneuver around bushes and obstacles pretty well and knows how to turn the bike off when he's done; He even tries to kick start the bike, but he kicks on the wrong side! He has no clue what brakes are, so I run behind him with a leash. All in all a pretty cool experience that I did not get with my two older kids.
