Just thought I'd pitch in on this old Lario string. Yeah - unmodded Lario's goes bang. I'm still riding mine with the mod often listed here. Restored another one last year with the same mod and riding her this year you yank out all hidden quirks.
A set of quality valves - Stein Dinse has good ones, a cam shaft with 14mm lobes and V7/Nevada progressive springs. I'm beyond Chucks 5000mile marker and my lobes look like new ones, and the mill spins up to 8000 rpm like a bat out og H***.
Not to start and oil string, but that IS important to a Lario and all other OLD SB's.
The word here in Europe among SB Guzzista are 20W50 or 20W60 with a viscosity index of minimum 150 and maximum 200. Closer to 200 than 150 is best. Important to the lobes and the oil pump, which seems to lose efficiency in the old SB's if the index is too low. Cam lobes does not like it either.
GuzziTech's V7 4V heads use the V7 progressive springs too. I think that counts for the choice. Give me a shout if you want to rebuild a Lario. I have a small document with the parts needed for the valve train rebuild.
Like Chuck said, it's one fun bike to ride on the twisties. Don't take her beyond 100Mph - then she gets a bit too lively - small 16" wheels base you know
Ciao