I just had the muffler off a week ago and it was fine. I'll check it again though.I've tweaked the timing both directions and it just makes it run poorly. I don't think it affected that knock.Fuel tank is nearly full.It doesn't knock like that unless under at least a little load so I can't really narrow down the exact spot. Perhaps I could enlist the help of a friend to hold the brake and give it a little throttle in gear...
I wonder if your points plate is hanging up your mechanical advance.
That's what I believe it sounds like, but I don't have much experience with these little thumpers. Try listening to it here: http://youtu.be/rXIzCynmCRM
Well, my noise and your noise sure aren't the same...Mine's much quieter and more rapid. Yours, alas, is slightly more alarming!
Well, it comes and goes sort of randomly.Have you checked your primary chain tension, or inspected all the stuff in your primary chaincase?
My stupid rattling noise ended up being a lose tank bolt. Metalic vibration noises at the top end of the gears right before shifting. DUMB ME. Spent a week trying to figure that crap out. Live and learn.