Originally Posted by kid_A
The advice to start out small and go from there, or play it safe with a 250 and upgrade later, should be taken with a grain of salt. If you're a moron who is going to hop on a bike with reckless abandon and gun the thing without feeling out the clutch/gas and get to know the actual power of the bike before flying down the road, then by all means you should start with a 250 and work your way up. Any responsible rider just starting out would be more than fine on a 650. This is coming from someone who learned on a 250 and was brow-beaten into thinking a 650 was "waaaaaay too much bike" for a first bike, and then got on a 650, rode responsibly, and realized that advice just didn't apply at all.
Umm...not if they can't pick up a 650...repeatedly...in the dirt, or get it to handle over rough ground and through trees, rocks, mud, sand, and the like. One may be able to start out on a 600lb+ 1200 on the street. Many do, but a 320lb+ 650cc dirtybike is typically a bit much for anyone not pretty darn big and/or strong to start out with in singletrack. A tall and heavy dirtybike with big/hard power and huge momentum is typically not as forgiving of noob mistakes as a mellow 250 that's under 300lb and a 35" seat. A DR650 is relatively light and mellow compared to most 600cc streetbikes, yet it has enough torque and weight to easily pound somebody into the ground if they get careless in the dirt.