Throttle return spring?

Hi,
I have not messed around with Lambretta engines since 1978 and I cannot remember whether the throttle has a return spring. Is the throttle supposed to snap shut when the throttle grip is released? Modern bikes do but I recall some old stuff doesn't.
Cheers
I have not messed around with Lambretta engines since 1978 and I cannot remember whether the throttle has a return spring. Is the throttle supposed to snap shut when the throttle grip is released? Modern bikes do but I recall some old stuff doesn't.
Cheers