Check out the pic of these carbs <!-- m --><a class="postlink" href="http://www.ebay.com.au/itm/Yamaha-FZR250-3LN-Carbies-/220956142175?pt=AU_Motorcycle_Parts_Accessories&hash=item3372032a5f">http://www.ebay.com.au/itm/Yamaha-FZR25 ... 3372032a5f</a><!-- m --> Are the two hoses that have the big plastic nipple things on them supposed to be joined together? There is a hose joining them together!
They allow air to move around the diaphragm inside the carb to allow the needle to open and close without restriction.