Small Engine Troubleshooting Problems? Ask a Mechanic Now.
Welcome to JUST ANSWER small engines, let me try to help you !! I don't know it all, but maybe together we can get you a satisfactory answer!
Sounds like BS to me! No way does the crankshaft bolt come loose on it's own, and regular checking of it is not necessary. I suspect it was not torqued when it was installed the first time.
Yes, makes sense, has to be specail washer and torqued , to stay tight!
It likley would have come loose, as the large washer would not be centered, and could cause vibration , and a poor fit, which can loosen the bolt.