Back in the early eighties, I had a problem with weave, I tried various tyre pressures, in particular, travelling to a Dutch rally. All to no avail. a couple of months later I was invited to a vintage meet in Burford. Oxfordshire. A gent came up sat down alongside and started chatting about the bike, unusually he had never had one, not even a Black Widow, anyway, I mentioned the the wheels would come out without the use of tools, and proceeded to take out the back wheel as a demo. Come to re-assemble, I find I cannot get the axle through, surprise I now found out the cause of my weave. The frame was broken, at the junction of lug and tube, with the weight of the rear end hanging, (D type stand) there was a 1/4" step between tube and lug.
So with a jubilee clip from a nearby garage, this was used to wrap the joint. We then rode home (100 miles) at our normal speed. I was not worried at all, after all, it was a bit better than before, and I`d had a couple of thousand miles of practice. But really it was the chain holding it together.
I`m trying to put a picture on, but no go.
Edit......... That`s strange it`s there when I look now. The picture shows the crack, before the clip was slid into place.