Sunny weekend here in Seattle… The kids are all out on their bikes in our neighborhood. One young neighbor seems like he’s living on his bike (better than in front of the tube!)
I was tempted to show him this great idea for making a motorcycle-like sound with his bicycle: I thought better of it seeing as he passes my house fifteen times a day.

You may already know an alternative method with a playing card or baseball card in the spokes, using a clothespin. Instead, try getting a balloon, one of the larger sizes, and fill it with a very small amount of air, to about baseball size. The excess size, uninflated will mean the rubber is more durable. Tie it to the strut on the non-chain side of the rear wheel so that it is free to flap against the spokes. As the bike is ridden it will make a very loud motorcycle sound. Best to do this for your nephews or nieces on a visit away from home…