This is a serious problem and can cause injury to your hand and arm! So you want to stop pulling on that pull cord immediately and have this problem inspected to determine what is causing it.
If the lawn mower has been repaired recently, the repair could have been done incorrectly. If you hit something with the lawn mower, then it has affected the timing of the engines firing and that is why it is ripping the cord out of your hand.
I fully understand this problem because I have had a pull cord rip from my hand and gouge in other hand that was on the handle bars.
Another thing that can cause this is a loose lawn mower blade. As the blade rotates, it will cause the firing to be off a few degrees and bam…that pull cord rips right out of your hand!
So as you can see, this is a serious problem that needs to be addressed. The problem will not go away or fix itself, so get your lawn mower into a shop and have it repaired correctly. Visit our Locations page for a shop near you.