hi and welcome !
yes there is a sensor and it maybe stuck or not plugged in
or perhaps the guy who had it before siphoned gas
or something & bent the float arm.
1.check the connector's connected and maybe see if there is any voltage there
2. get a clean wire some what stiff and put a hook on it and see if you
can snag the float arm and lift it~ see if the gauge moves.
3. if voltage at connector and no change at the gauge when you lift the float
with the wire ~ you might need a new sensor. let me know if thats the case
i don't think its the gauge itself since you say it moves and you will confirm
when lifting the float.
oilyhans
i own a scooter shop with rentals ,sales& racing parts.
i also appraise scooters for KBB.
2003 Vino classic stage 0.75
de-reged stock variator w/8g sliding weights.
1.5k rpm springs
42mph
2005 veniceLX ~70cc~upjet~1.5k rpm springs & 7gr sliders
46mph
KeyWest de restricted~8gr slide