My 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 pedals and rode with him. 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 long bike rides. he on his balance bike, me on pedal bike. (I kept the pedals off for 2 weeks and we rode daily).
A good model and the want to do same was key.