Dellorto part number 8533 (PHF 30/32/34/36 top cap )
Moto Guzzi V700, V7 Special, Ambassador, 850 GT, 850 GT California, Eldorado, and 850 California Police models
Thanks to Charlie Mullendore of Antietam Classic Cycle for posting this on the old Yahoo! Loopframe_Guzzi news group (which has now moved to Groups.io).
The dimensions of the are 2 mm wide × 38 mm ID. A suitable replacement is McMaster-Carr part number 9262K201. This part is also available directly from Dellorto as part number 8533. Or, it is included in the standard carburetor rebuild kit, available from MG Cycle.