Recently I had my low mileage 1974 850 crankshaft crack tested and it failed. There was a microscopic crack around 30 % of diameter of the shaft at the right angle from the drive side main bearing shaft to the drive side "porkchop" . I use the words right angle because that is exactly what it was - and in the words of a mechanical engineer and 30 years experience in the materials lab of the old NZ Physics and Engineering lab of the DSIR - one of the best examples of exactly how NOT to machine a change of section he had seen. Direct quote " Those damn Brits should know much better than to machine a crank like that in this day and age. " I pointed out to him it was a 1974 machine and he said - " I mean in the 20 th century !!!!!!!! " They learnt not to do that making railway wheels in the 19 th century !!!! " I have since inspected a few more cranks and " Yes they are all like that Sir !!!! Its pretty common for Norton cranks to break at the big end after a regrind if the correct radius has not been been ground but engineering shops here know that and do it properly. And perversely the timing end does have a small ground radius from the porkchop to the shaft. But not the drive side !!! The inner races of main bearings have a small radius ground in them to allow for this so who knows why Norton didn't bother on the drive side !!!!! I have two options I'm currently following. The first is a new one piece billet crank which is having its own issues but not the subject of this post. Plan B is a second hand crank I have bought. Right now it is being crack tested. If it passes - engineering friends have suggested the following: Machine in a small radius at the drive side bearing shaft to the porkchop change of section. Mask off the shafts and shotpean the change of sections Possibly consider nitriting ? Reassemble with new hardware, check dynamic balance, run out etc and then install. Has anyone had any experience with this and any further suggestions ? I'm not planning to race this bike but I also want total peace of mind and am prepared to pay for it. I do not want to take this engine apart again.