'09 Vstar 250 sprocket replacement

First off what are you wanting to do? Are you wanting to lower engine RPM at Highway speeds or performance stoplight to stoplight? To Lower our RPM you'll need a sprocket with fewer teeth at the rear, more at the engine or both. Don't know whats available, but by checking into your bike nomemclature you should be able to to know where you start. Doing just the front will probably involve less cost and you may be able to use your existing chain if still serviceable. If you figure the ratio of front sprocket to rear you can use this when you determine how much you want to lower your cruise RPM to buy the the correct sprocket or sprockets to get this reduction.
However now I offer a disclaimer. If you lower your cruise RPM your pick-up will suffer some. It's kind of a balancing act holeshot versus cruise. I say lower your cruise RPM, get a cam, a pipe, open up the intake and re-jet to get back that lost power.

Yes, I was wanting to lower the rpms at higher speeds. How much would it affect my start up acceleration because for now I've got more than enough to work with.

How high is the RPM at cruise? What would you like to bring it down to?

The v star 250 doesn't come with a tach but at 60mph its pretty high, but from the things ive read around these boards replacing the sprockets will turn my 60mph 5th gear rpms to basically my 60mph 4th gear rpms

None of the V-stars do, didn't know if you had one or could rent or borrow one. Here is a link to some ratio pairings to help you decide where you want to be.

http://www.cyclechaos.com/4um/f27/virago-250-front-rear-sprocket-upgrades-15285/

Hope this helps. The v-star and virago in this case the 250 are pretty much the same engine and stock ratios of 16/45

Awesome, thanks! Wondering if I would need another chain or not, probably though.

Depends on where it is adjusted now, but if you do both sprockets and your chain is serviceable then probably not. From what I saw on that page you were going up 1 or 2 on the front and down by as many as 7 in the rear, sounds like you might need a chain breaker to shorten it (take a link out). By all means try it first.