I have an issue with my starter. It's a 1650. When I turn the key the starter turns and the outer gear engages the flywheel, but does not turn the engine over. I can hear the starter turning, and it appears that when it gets to this point the shaft is spinning. When I took off the starter and worked it by hand, everything seems fine no binding turns easily, and returned easily, until the spring broke. I did notice that the battery was only putting out around 10.5 to 11 volts. Could this be the cause or should I be looking at something specific with the starter?