I was able to fix my FX 25 with the same pull cord problem. I ordered parts through a company called Small Engine Parts Warehouse.com. You need order the spring that sits under the rope pully. The part number may be different for your FL 25, but this company can help. The part number for the "starter spring" on the FX25 is 545008010
The web link is http://www.smallenginepartswarehouse.com/home.asp
Hope this helps someone. This was a very easy process. I would suggest wearing safety glasses while handling the spring. It is wound with considerable tension. If you jar, or drop this part it will likely un-spring and could cause injury. There are no instructions for this install that I could find, so here's my attempt to explain it.
To disassemble, open the weedeater case separating the case to access the rope pully assembly. Carefully remove the two black retainer clips that secure the rope pulley and silver spring assembly that sits below it. REMINDER!!! Use caution when handling the spring. It is wound tight and could unspring if jarred or dropped.
To install, place the spring assembly into the weedeater housing so that the silver side of the part is towards the cord pully, or facing you, or up. Be sure to get the outer tab of the spring seated in the grove in the lower part of the weedeater case. There's only one place for the tab to fit.
You will need to remove the black handle from the end of the rope and pull the end cord through the hole in the case. Wind the cord around the cord pully in a clockwise direction. Leave approx 1 inch sticking out. Hold the end of the rope so it doesn't unwind and gently slide the rope pully, with the flat side down, over the spindle. Be sure to seat the rope pully all the way down into the spring. You must be aware of the positoin of the spring end as you slide the rope pully down. It needs to mesh with the spring. Prior to attempting to install the rope pully, be sure you can see the end of the spring through the hole. Once you have the rope pully fully seated, you should be able to re-install the black retainer clips. Be sure, prior to installing the retainer clips, that you have feed the end of the rope back through the weedeater case. I held the rope outside the case with a spring clamp while I re-installed the retainer clips. Once the clips are installed, re-attach the black handle to the end of the cord. Finsh putting the rest of the case together and you should be ready to go. Good luck!
Craig
August 2009