How do I rewind my starter rope?

The problem with your pull start is that you did not rewind it enough. You need to rewind the length of the pull cord plus several more turns of the internal spring to have tension on the cord even wile it is retraced.
Usually another 2 to 4 turns.

I do not know if you removed the pulley to rewind your cord but just in case I added the procedures to do the rewind.
Hope this helps

Some pull starts can be rewound without removing the pulley unit but the correct way will require you to remove the pulley unit. Also it's a good idea to replace the cord with a new one otherwise it's just going to break again, sooner rather then later.
With the pulley off and looking at the back side rather then then side that faces out. you will see a pulley. you might also see the coil spring. the idea is to turn the pulley until the cord is completely retracted. Mark the spot where the end of the cord is on the pulley because you may not be able to see it once you have it rewound. Now you need to continue turning the pulley or in other words tightening the spring. As to how many turns, that's kind of trial and error. Start with 2 and then try it. You want it to retract and still have tension on the line. Now find the mark showing the end and rotate it to the exit hole. It can be helpful to melt the end of the cord to prevent fraying and make it easier to feed through the hole and tie on a handle. Another good idea is to use a small piece of wood with a hole drilled into it. Use this until you have the pulley tension right.
Depending on the style of pulley it may also be possible to rewind the spring first then feed the line through the hole and attach it to the pulley.
Good luck!

Hi you need to wind the spring to put tension on it depending on the type of recoil starter it is faily easy or dam near impossible "nothin is impossible "
take the compleate starter assembly off the motor and undo the rope from the starter / fit a new piece of rope 12 ins longer than origonal turn the center piece anti clockwise 2 turns ,this will wind the spring up wind the new rope on to the pulley put the handle on so you can feel it pull back and knot it so it has tension on it hpoe that helps merlin v12