> "In the race it was quite definitely faster than the Nortons and I had little problem getting past Geoff (Duke) and Ken (Kavanagh) with just three Gileras only a short distance ahead," Rod recalls in his book, The Colemans. “I did get with them and found again that the Porcupine was just as fast as the Gileras but was down a little on acceleration from the slower corners, but not by much. I was just beginning to think I had every chance of second place behind Milani when the motor stopped.” The cause was yet another magneto shaft failure.
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> Read more: http://www.visordown.com/motorcycle-new ... z1MZ2YTboF

Twas a pity superchargeing was banned post-war .

Pre 56 K2F mags had a smaller bearing at the gear end , the brass armature end had a pressed in stell shaft , with the taper for the drive gaer.
Post 56 theres a larger Dia. so the walls a bit thicker than 1 m.m.

The dreaded SR2 mag , developed from the Massey Feguson tractor Mag. had a rotating Magnet and fixed Armature , so as to have less inirtia .

Maybe the Porcipine was a bit lacking in flywheel , sans supercharger. The instantaeneous R.P.M. change overstressed the shaft, hence failure .

Thanks Matt for further education that's over me head but for the part of dropping supercharging in major motorcycle power developments. I do miss some of the styles of yesteryear.