Correct idle speed?

[Hellcat]

The owner's manual says idle speed should be 900 +/- 100. But the speedometer has a little mark at around 250 that would appear to be an idle marker, and that's where it was set when it was sold to me.

[CajunRider]

250 is way low. 

500 is the first area where it starts to idle smoothly.

800-900 is where the alternator is able to keep up with the lights and keep the battery charged.

[DeathWishBikerDude]

900 rpm is the factory reccommendation.
I run about 700 rpm,as it saves me some fuel,and the neighbors don't wake up every morning when I leave the house.
900 seems too high,as sometimes coming off the highway,the idle can flucuate over 1000 rpm.

[Chrisj CMA]

This question comes up periodocially......First Turn the idle up to somewhere around 1,000 rpm before you deprive something of oil. 

All my previous bikes were to idle above 1000 rpm, so 900-1,000 is fairly low to begin with

Its the sound that makes people think its fast, you will get used to it

[Willow]

The owner's manual says idle speed should be 900 +/- 100. But the speedometer has a little mark at around 250 that would appear to be an idle marker, and that's where it was set when it was sold to me.

The first mark on the tach is about 500 RPM even though it's not in even segments at the low end.

800 RPM is plenty for idle.  I charge my battery while I ride.  I don't plan on sitting all day at idle.  Wouldn't be a good idea for reasons other than the alternator's need.