Carb retaining nuts

If you can get those with a reduced hexagon as used on the Dommies.

You need Nyloc, or 'Stove nuts' - the ones where the top is slightly 'crushed'. That way they stay tight without overdoing it and you don't end up buckling the carb flange.

As to thread, my thoughts are that they are 5/16" BSF, but happy to be corrected.

Regards, George. 

I think they are Cycle thread, I’ll see if I can have a look later.

... have the reduced hex type. You don't need nyloc - just use a single spring washer (not the serrated ones) and tighten till it just flattens. This is enough to stop it coming undone but not enough to distort the flange.

Oh, mine are 5/16" Cycle thread but it's wise to check as the studs may have been changed at some time.

The old part number was E3231..........now apparently updated to 067589.