If it is one of the ratchet starters as below:
[Linked Image from ecx.images-amazon.com]
Then the center drive can be slightly bind to crankshaft. Sometimes all is needed is oiling thru top hole to re-lube the felt pad. Other times the top of the crankshaft is damaged and require filing down the high spots that is causing the binding.

I have seen these to be screamers and even destroy the recoil springs when they are binding.