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most people say dont start on a 600cc... but thats just the general rule. its all dependent on the person.
my friend has ninja 650 and he can wheelie it no problem, first and second gear. my friend has a 250 and he can wheelie that too. so if thats what your looking to do, you can get a smaller bike. and the 250s and 650 are about the same height at as a 600.
i, for one, started on a 600... that was about 6 months ago. saw a lot of my friends do the same. (and one started one 1000cc ducati, but he is an idiot). i seen a lot of people go down, less so on smaller bikes. i got rid of mine because i got too cocky and the car i have wanted for a long time was on the market.
and with a 600, if a car merges onto you and you accidentally jerk that throttle, your going right off the back. and people merge on you on a daily basis.
so.... pretty much buy great gear. you will go down.