How do I fix my lawn mower if the pull cord is catching on a white stopper inside the housing?

It appears like a safety mechanism that only allows the pull cord to go a few inches before stopping the rotation. The white piece can t be seen until it extends out from the center of the recoil assembly. This is a Yard Machines 21" 163cc push lawn mower.
Answers

Spock (rhp)

see the repair manual -- it's likely online. you'll probably have to disassemble the start mechanism. sometimes putting those back together again is a pain

Johnny

Ok you must first remove the housing, then get the white stopper with some pliers and turn it anti clockwise. Once this has moved two thirds and an eighth of a turn (you gotta be really precise) it should unlock the jism nut. Take out the jism nut and give it a good polish, something like a loose onion is also in there but dont worry about that its safe now. Take the jism nut and hold it tight between your forefinger and thumb. Then with your spare hand slap the back of the hand holding the jism nut. This should release the nut from you grip allowing it to fall freely through the air into the regions of the ground you aint seen for years now once you have it all apart put it outside in a pile and there you go. Happy Sunday :)