Well Grandson got one at 2. 
He was interested but only for a few minutes at a time. Then Gramma brought up her bike. took off the peddles. and rode with him. As he did exactly as i did. no coaching. he just got it. He is 2.5 years old now and we can go for hour ling bike rides. he on his balance bike, me on peddle bike. (i kept peddles off for 2 weeks we rode daily).
A good model and the want to do same was key.