I've just find an interesting page about Gilera 50'/60' carburetion data: and I've find too this website where you can find:
Gilera 150 informations,
Gilera 175 parts manual (!!!),
Gilera 150/175 Repair Manual
(see down in this page).
http://www.flickr.com/photos/seat850/co ... 317671452/
Have a nice day!
Ciao
Marco