scrape of the varnish off of the spring eye which may also have been glued work from the top of the spring eye with the point of a needle to locate the end of the spring prize away from bristle and unravel the spring take care otherwise you may damage the float body gently sand away any varnish from the part of the bristle covered by the spring eye to remove any varnish /glue and reseal with matt varnish, select the ordinary eye to insert in the side off the float however use a micro drill bit to ensure a nice clean tiny circular hole putting a pin into the side of the balsa may split the balsa and render the body useless so use a micro drill bit, having drilled the hole locate the side eye if carp float I like 0.20 wire extra long eyes wilkes on ebay will supply you these and you can cut the length that you require with wire cutters if they are too long glue in place with a good waterproof glue and then varnish twice to ensure no water can enter the body.
Failing that just spend £1.50 on a new hand made float! job done