Hi FiM

Not completely sure what motor you have without seeing it but sounds like the one with those older Briggs recoil setups, that the clutch pawl or ratchet sprocket acts up, works just like a bicycle freehub—if the little dogs or springs get gummed up, worn, or fail to disengage, the spinning flywheel catches the starter and forces the cord back out at a million miles an hour, generating enough friction to melt the plastic housing and fry the ratchet.

You can buy a new inner starter part that threads onto the crank, if you can find one, but usually these have small steel balls inside to
engage ,if its not too stuffed I usually open the seal up enough with a feeler gauge on the ratchet part and spray WD40 into it , you aren't
meant to as this makes it slip but if you spray it then leave it a day its usually dries enough to work but is lubricated enough to stop the squealing
and ripping the rope starter apart.

I usually find if I replace them with another second hand one it does the same thing until you use WD40 in it.

Cheers
Max.