I think that's about right. From what I recall (from looking at Owner's Manual), there're 2 different idle speeds: for California model and for a "normal" model. I think that "normal" one was 1,5K and the CA is 1,8K
Do you have the owner's manual? It tells you all those numbers and the proceedures on adjusting idle, if needed
another thing to keep in mind is that the tachometer (like a speedometer) isnt 100% accurate. so if your tach says 1500rpm that doesnt mean your engine is going exactly 1500rpm. i think idle speed should be the lowest speed that your engine idles well at, thats how i set mine.
If you look in between the carburetors...there's a black thumbscrew between the two of them. That *should* be your idle adjustment screw. The idle mixture screws can also affect your idle speed....those are small screws on the bottom of the carburetors pointing directly up. Turning them right leans the mixture, turning them left richens it. But unless your screws have been adjusted before or the bike idles poorly now with aftermarket parts, I wouldn't touch them.