13T front sprocket for Lambretta J50 + Lui 50 models (+ tuning)

13T front drive sprocket for Lambretta J50 + Lui 50cc models (for re-gearing when tuning).

This is the complete list of all possible front drive sprocket & clutch crownwheel sprocket combinations for all J-Range and Lui-Vega-Cometa models, complete with the required length chain (with 'live' product links):

45T Clutch Crownwheel Sprocket
45T clutch sprocket + 11T front sprocket = 73 link chain
45T clutch sprocket + 12T front sprocket = NO! 
45T clutch sprocket + 13T front sprocket = 74 link chain
45T clutch sprocket + 14T front sprocket = 74 link chain
45T clutch sprocket + 15T front sprocket = 75 link chain
45T clutch sprocket + 16T front sprocket = 75 link chain

46T Clutch crownwheel sprocket
46T clutch sprocket + 11T front sprocket = NO!
45T clutch sprocket + 12T front sprocket = 74 link chain
46T clutch sprocket + 13T front sprocket = stretched 74 link chain
46T clutch sprocket + 14T front sprocket = 75 link chain
46T clutch sprocket + 15T front sprocket = 75 link chain
46T clutch sprocket + 16T front sprocket = 76 link chain

47T Clutch crownwheel sprocket
47T clutch sprocket + 11T front sprocket = 74 link chain
47T clutch sprocket + 12T front sprocket = stretched 74 link chain
47T clutch sprocket + 13T front sprocket = 75 link chain
47T clutch sprocket + 14T front sprocket = NO!
47T clutch sprocket + 15T front sprocket = NO!
47T clutch sprocket + 16T front sprocket = 76 link chain