The only secret I know of is patience.
When I had to do mine, this is what I ended up doing:
1. Clip the damaged end and rebend it to get held in the center slot on the reel. I even added a little double bend that would compress and act as a wedge to keep the spring from pulling itself through the plastic slot as easily.
2. Pop the little Hyper 21 medallion off the back of the pull start case from the inside. It is held on there by some pretty cheap glue, but I would still try heating it up in some boiling water to minimize the damage to the medallion.
3. Recoil the spring as tight as you can. This needs to be done outside of the case. The insert the U shaped portion that starts the outer ring of the spring into its retaining slot...very carefully so the spring doesn't get sprung.
4. Release the spring inside the case carefully so that it unwinds coiled inside itself within the confines of the back of the pull start case. (I'd show an image but I don't want to disassemble my pull start to take one...trust me I feel your pain).
5. Now coil the pull start cord around the spool, and feed a little bit out of the grommet that passes the cord from inside to outside the case.
6. Grab a pair of needle nose pliers (really thin small ones). Poke the nose of them through the hole in the back of the pull start case (the hole that gets revealed when you removed the medallion). Use the needle nose through that hole to hold the spring in such a way as to allow the slot on the spool to catch the spring when you re-insert the spool. This will take a few attempts (more patience needed here...trust me).
7. Once you have successfully got the spool inserted and it has engaged the spring, you should just have to replace the medallion (I used medium CA glue for that purpose). Then put the handle back on the cord, and re-install it on the engine.
8. FINAL TIP: Just buy the replacement pull start or send off for the free replacement. It may take just as long to get the new one as it will take you to repair this one. Just kidding.
After about an hour of trying, I did get my pull start back together, but ended up following step 8 to get my free replacement. Always a good idea to have a back up.
