Hi Folks was working on carburetor on vespa gt 200,the problem wasn't the choke but on inspection of the choke noticed there was 3 or 4 threads showing on the casing,now I always thought the choke was set and there was no adjustment so I thought it had unscrewed, having screwed it back in the starting became harder so I unscrewed it leaving 3 or 4 threads showing and the scooter started first time again, so in conclusion the choke seems to be adjustable, if you are leaving a few threads showing on the case technically the needle is higher up so gives a richer mixture or is there something else at play? Cheers