After while the one way bearing starts to lose grip and starts to slip. (Hey what a rhyme). Anywayz on the serious note, all pull string bearings will eventually go out. Cold weather can also cause it to slip. So from now on I'd reccommend you to spend the money and get a non-pull start engine and a starter box. Because you'll probrably go through like 4 pull starts before the life of the engine is finished. If you continue to get engines with pull starts you'll be spending a lot of money, especially if you run your car often. And pull starts cost like $35 dollars. And actually the engine will run a little faster and smoother without the resistance of the pull start bearing. That's why you never have seen guys who race have pull starts. Another thing the engines that are made now has a lot of compression. And after pulling on the string time after time the string will eventually break.