I think the float spring is in the float valve, and not replaceable, it's a very small plunger on top of the tiny lil float valve, there are several different vendors but stock is a Keihin 18-8955 best price is on amazon, $5 less than the jets r us price. this video may be helpful.
I have just been doing my homework because I am about to do my first carb job. These video's don't represent the amount of parts you get from "Redeye" kit because he doesn't separate the carbs.
https://www.youtube.com/watch?v=7rtNABYbpmk