Have you done a carb cleaning yet? I just ask because when doing a good cleaning you can inspect for things like this.
When doing the cleaning I suggest you take a Q-tip, peal off the cotton and wrap with 4/0 steel wool. Use this with fingers only. Insert into the float needle seat. Spin, this helps get all the old fuel deposits out of the seat as well as remove any burrs from new.
If you do decide to clean your carbs
www.amckayltd.com/carbguide.pdf is a good read. I suggest you read it, print it out, read it again. Then using the carb guide follow the steps to tear down, clean, inspect what you have. Once you determine if you need any parts then buy what you need.
Most kits come with a set of generic internal parts. This basic carb had many variations and was used on many bikes. Those generic parts may work with some bikes but not the XS650. Doing the tear down, clean and inspect first can save you money.
Leo