greg bender
http://www.thisoldtractor.com/gtbender
NOTE: In general, I do not recommend turning the brake drums on these machines. But, occassionally, it may need to be done. I would certainly never perform this as part of any "routine" maintenance.
Thanks to Locky who posted this information on the Yahoo! Loopframe_Guzzi news group. In (mostly) Locky's own words:
...in regards to your question about the specs for the brakes, what I think the brake shop is after is the internal diameter of the drum. I'm not sure about a 2 leader brake but the 4 leader is 219.900 mm - 220.000 mm or 8.657 - 8.661 inches. The brake shoes need to be turned while fitted to the backing plate to 219.880 mm - 219.950 mm or 8.653 - 8.659 inches. But they need to be turned while the cam is in the open position and the cam operating lever at 119.800 mm - 120.000 mm or 4.716 - 4.724 inches from the anchoring lug. That will make sure your break shoes are the same radius as the internal hub when the breaks are applied. The measurement to lock the leaver to is taken from the back of the lever where the cable attaches to the back of the cable anchoring lug. You will have to make something to lock it in this position then have it machined, and that how its done. Hope this helps, Locky.