Crank balancing

Try Basset Down in Swindon, as they have been doing this for a very long time.

... it has the correct radii on the ends of the regrind.

If I am not mistaken, the 650ss crankshaft size is 1.75 so it is the same as the Norton Atlas and the Commando crankshaft. You can see if there are -10 Atlas or Commando big end shells.

A couple of months ago bought 'em from Andover Norton. Same for 650 and Atlas. Mine also had to be reground -.010. Done with correct radius. It's wise to also check that conrod big end isn't oval and need machining. One of my conrod small end was a bit too loose fit, had to be replaced.

Hello well, I had mine done at Arnett engineering Doncaster   There was No need to rebalance with - 10 UNDER SIZE     NOW CHECK  IF YOU OIL PUMP  is 3 start or 6 start as if you have a 3 start oil pump there is No NEED for OIL HOLES in the Shells   or you have more problems    yours   anna j  

Forgive me if I’m reading your post incorrectly but -10 refers to the new diameter of your big end journals after regrind (ie now 1.740” rather than 1.750”).

The shells to go with this are also -10 rather than +10 as the internal diameter of the shells is similarly reduced to match the reduction in journal size.

Regards

Peter