OK, it's no secret there are lots of Questions about jetting! So I thought I'd do an info post on the basics with a few pics and some explaining to go along with it. I have an extra set of carbs off a 2009 Ninja 250r. They are the same from 2008-2012. It's gonna be a few posts as I seem to be only able to post I pic per post. So first pic here is one of the bottom of the carbs with the float bowls in place.
Second pic is with my finger pointing to the idle mixture screw. When the carbs haven't been worked on these screws will be covered with a metal plug that has to be drilled with a small drill bit and then quite often a screw will be used to pull out the plug. Don't worry about replacing the plug. This screw is usually gently turned down to the bottom and grounded while counting how many turns that takes just for reference sake. Then quite often for a stock bike it would be turned back out from ground 2.5 turns.
The black section is the sensitive rubber membrane part of the vacuum slider. Gently peel it back around the round edges, you don't want to tear it! Then you can remove the vacuum slider and the fuel needle. The shiny part in the center that I'm pointing to is the top of the fuel needle.
This is the vacuum slider removed. That's the rest of the fuel needle sticking out the bottom. Note when cleaning carbs the vacuum sliders should be removed and kept far away from any carb cleaner! The rubbers can be easily damaged.