I check my nuts and bolts every other ride. If I take a long ride I will do it every ride. I went through my check list: shake the engine see if it's loose, feel the pulleys, check the nuts on the all thread, check the spring and finally pull up on the clutch.
The clutch pulled in far too easily. I looked at the engine and did it again, one of the cross braces- the one on the end had loosened enough that it was alarming. It wasn't noticeable when I shook the engine because I shake it UP and DOWN and not side to side. The screw/nut that hold the engine to the side and holds the brace in place as well had come substantially loose. I tightened them all and they held up just fine for my smooth 5 mile cruise last night. I suspect that the faster I go and the bumpier the ride the more loose it will get.
I checked them again last night and no problems. But on Sunday I did 22 miles.
Yeah so now I check the nuts and bolts every ride and bring a good tool kit with me- just in case!