650ss Primary Drive Case and Lower Gearbox Bolt woes

Check Dommie Service Notes page 153

The nuts that I think you're talking about are 7/16 inch cycle thread (20 tpi). In the past i have managed to cut a nut in half with a narrow hacksaw blade and lock the two halves together to remove the opposite nut.  If I'm not mistaken I used a 7/16 inch UNF nut which is wider than the Cycle but is still 20tpi.  It looks as if someone has used a reduced hex 7/16 inch nut at sometime.  You should be able to free the offending nut then and remove the inner chain-case bottom bracket from the stud.  Run a thread file across the threaded portion of the stud before refitting the nuts.   Cheers, howard

Can't offer advise on getting the nut free, but once you have solved that problem and eventually got the inner chaincase off, might I suggest the following mod to the steadying tab.Cut out the bottom of the tab so that the hole becomes a slot. Once in situ, providing you can loosen a nut on one side or the other of the stud a thread or two, the chaincase can be wriggled out of place and back in afterwards.

I have 2 old inners with this alteration, and I don't see it having any detrimental effect.

While its to bits ,completely remove the top bolt  to clean and grease otherwise sometime you will have it seize in the alloy of the box. Another horrid job which can entail removing the gearbox AND engine to fix.You wont know its seized untill  after about 10 failed attempts to adjust the primary chain and perhaps some wrecked engine or gearbox bearings . All for the sake of a smear of grease.