Scooterotica

just jetting my 25mm delorto on my 175, running an 100 main jet and its spot on (102 bogs) like you when shutting off from full blat it was racing a tad, try raising your needle by dropping your circlip one notch , should cure it.

Assuming no airleak could just be idle mixture adjustment. Try turning the airscrew out a turn or so, if this doesn't help try going one size larger on the idle jet and adjusting until the engine returns to idle fairly quickly when throttle is blipped. Hope its that simple.