Engine size isn't really a good guide. A CBR600RR, GSXR600, YZF-R6 or ZX-6R are all around the 600CC mark, but with power outputs over 120 HP and steep power curves, probably aren't a good first bike.
You'll likely have poor throttle control when you start and in a corner you could easily put one of these supersports down in a low side.
Whereas something like a SV650 or MT07/FZ-7 may have a larger engine than the mid range super sports, but with around 70 HP, but still good torque outputs and a much more friendly power curve would be an ideal choice for example, both are still quite sporty and fun in corners and open roads.
OP depending on what style of bike I'd start with something between 250-700 CC whilst specifically steering clear of the super sports and high strung nakeds like Street Triples or Ducatis (all too fast for someone with no experience), and also stearing clear of 125 CC bikes (too slow and even a total beginner will outgrow them within weeks without much carry over in skills to a bigger bike.. or worst case you'll be turned off bikes altogether when a family van overtakes you).
Eg cruiser: 250CC Yamaha Virago or the 650CC Yamaha V-Star, 400CC Honda VT400 etc.. get experience, some advanced training or some sorts and then upgrade to the big cruisers like Harleys, VMax etc..
Something sportier: 250CC/300CC Kawasaki Ninja, or in the 600CC range something like a Suzuki SV650 or Gladius or GSX650F, Yamaha MT07, Kawasaki ER-6N or Ninja 650. Get experience and advanced training then get a supersport or big capacity naked bike.
You'll likely have poor throttle control when you start and in a corner you could easily put one of these supersports down in a low side.
Whereas something like a SV650 or MT07/FZ-7 may have a larger engine than the mid range super sports, but with around 70 HP, but still good torque outputs and a much more friendly power curve would be an ideal choice for example, both are still quite sporty and fun in corners and open roads.
OP depending on what style of bike I'd start with something between 250-700 CC whilst specifically steering clear of the super sports and high strung nakeds like Street Triples or Ducatis (all too fast for someone with no experience), and also stearing clear of 125 CC bikes (too slow and even a total beginner will outgrow them within weeks without much carry over in skills to a bigger bike.. or worst case you'll be turned off bikes altogether when a family van overtakes you).
Eg cruiser: 250CC Yamaha Virago or the 650CC Yamaha V-Star, 400CC Honda VT400 etc.. get experience, some advanced training or some sorts and then upgrade to the big cruisers like Harleys, VMax etc..
Something sportier: 250CC/300CC Kawasaki Ninja, or in the 600CC range something like a Suzuki SV650 or Gladius or GSX650F, Yamaha MT07, Kawasaki ER-6N or Ninja 650. Get experience and advanced training then get a supersport or big capacity naked bike.