Handlebar clamps gap should be close to even, not like my HD's front wheel clamp where you tighten one end of the clamp fully and then leave a gap on the other end when tight.
Edit: How tight, tight enough the bar doesn't move. You don't need it any tighter.
You may have to look at an older manual for your bike, Guzzi is known for leaving out info that was already in a manual. Alto try Benders site for the torque spec.
Edit: If a previous manual told a mechanic how to take apart a transmission, the current manual will just tell you to take it apart. Being a trained mechanic, you should already know how to take it apart or to look at the previous manual.
Tom