You're right, but so few people care about that and even less can tell the difference. The S up to 07 (I think) had a 44 tooth rear sprocket. The N had a 45 tooth rear. For one or two years they both had 45's, and then the N went away. I'm pretty sure current S's still have 45s.I think there is also a difference in chain length and sprocket combos resulting in slightly different gearing between the S and N models. This may also be unique to specific years.
Didn't know about the shifter. Thanks for the info.I know of 2 of the differences. There may be more. One is the shifter pedal. It's connected to the footpeg instead of having it's own shaft and the rear subframe is different.
X for 1999 and Y for 2000?SV650 - Refers to both models (S and N) of the SV650 platform, but also used to refer to JUST the N model
SV650S - Bikini fairing model with clip-ons and more aggressive seating position
SV650N - Naked model with handlebars and more relaxed seating position
SV650SF - Full fairing model with clip-ons and more aggressive seating position
SV650SU - Australian version detuned for less HP
SFV650 - Suzuki Gladius
SV650A or SV650SA or SV650SAF - Anti-lock brakes on the aforementioned models
Edit: The K, as mentioned, is the year designation for 2001+ models (I forget what they did for 99 and 00). It's added on to the end of the code, as in SV650SK3 for a 2003 S model.