[Dadhawk]

I think some of it depends on the style of bike as much as the engine size. As an example, my youngest son is showing an interest in riding so we are talking about it.

I would have no problem with him having a 600cc or even more bike if it were a standard/cruiser/touring type bike. If its a sport bike though, we are talking 250cc and only because they don't make them smaller.

Main reason, because race bike.

It's the same reason I let him drive my 5.3L Suburban to school but do not let him drive the FR-S unless I'm "around". It's just asking for trouble.

Even as a "mature" first time rider, you are going to be much more tempted to do stupid things if when you walk up to the bike it speaks to you and says "You are a riding god, you know you can do this, come on, just once!"