We've had a lot of cases of flywheel nuts coming loose and creating all sorts of havoc. It's been caused by out of spec threads on the stock nut. They can come loose even when slathered with loctite and proper torque. Nichols Manufacturing has a set of locknuts that replace the stock nut and solve the problem. Here's their website link:
http://www.nicholsmfg.com/ They are located locally and I deal with them often. Good people and excellent products.