I’ve heard the story too, but I’ve no idea if it’s true. Anyone on here have first hand experience of such failures?
Dave Degens told me he had never stripped a 650/750 Triumph engine due to main bearings failure!
Norman Hyde’s version of the story is that this failure mode occurred during development of the T140, not production bikes.
And he said it was “failure of the welded cage T/S main ball bearing” that was the issue, not the drive side roller as mentioned in the video.
Even if it is true I suspect something else was at the root of it, a faulty batch of bearings? Incorrectly machined cases? Etc.
There’s are too many tuned Triumphs flying around. We all know they can break the crank, throw a rod, split the cases, etc, etc, but main bearing failure just ain’t high up on the list IMHO.