Could very well be the OWB .. BUT .. before you buy one, pull the bearing off and try turning the shaft to see if it will turn the motor. It could be the small spring and pin behind the back plate. The spring likes to break ocassionally. OWBs are alot cheaper on e-bay or there is a thread somewhere about being able to get just the bearing itself and pressing the old one out. I think it was about googling the bearing # stamped on it. The spring is in the end of the crank. I found the a toothpick with some grease on it will pull the spring out. It is small. maybe 1/2" or a little less. It pushes a small pin out to the start shaft to lock it for directional starting. Don't lose it ! Kinda hard to explain, hope this makes sense.