Sprint 125 125Cc + Pinasco Alu 177 settings and next steps

Hi

First post for me and yet pretty novice in vespa mecanics

I acquired back in June A vespa Sprint 125Cc (VNL2T). On it I put 

- Pinasco Alu 177 2  transfers

- Sip Road Exhaust

- Kit polini Venturi

- Ignition 18°

- Bosh W3AC

- Carb Si 24/24 with BE3-160 + Idle 160/155 + Main Jet 140 provided with the venturi 

- Adjusting mixture screw tourned backward for about 2.5 turns (after screwing it to the max)

I drove about 500km at 4% and after 3% full synthetic racing Castrol Oil 2T for about 500km more, so total 1000km driven. Max speed reached 100km/h from the vespa speedometer but not confortable at all. Crsuising speed 80/85Km:h is comfortable and forth gear most of the time and even can start on Second!

When I bought the scooter the bootom part of the engine has been refreshed with new rolling, joins etc BUT no new cranks and no modification on admission

The scooter is running fine, start after 1 kick start but yet I feel like the carburation is not set propoerly and that the pinasco is not revealing all is power. 

After checking the spark blug regularly it looks black and sooty. this means that this is too rich, right?

So my question is more related to the fine tuning of the car which is the most difficult part.

What would you recommand to get the best carb settings and get the best performance. reducing the main jet or other?

I'd like to add that I just have a Touring use of my vespa and I am just looking for liability on the long run using the confort of the pinasco

Thanks a lot for your feedback

PJ