I had similar grief with a downpipe intended to "fit" my Velocette Viper from Armours... I too made the mistake of fitting a long time after purchase..
The head end the tube is too large a diameter & so it blows there.. The mounting bracket was not welded straight so it took a good friend with a milling machine to modify the slot so that it would be in the right area for the mounting bolt, followed by some brutality with the socket + bar to bend the thing into the correct place when tightening it up...
Velocette design barely changed in 30 years so there's no argument that my bike is "different" ,they should have got this right..
Some people seem to have had less trouble (eg a mate with an AJS). Maybe they're better at some marques than others, or maybe their quality control is cr*p...
Either way I'll be going elsewhere for the bits I want for my A10.
Cheers,
Adrian
