Scooter slow clutch engagement

Hello,

I don't really know much about scooters, but the basics.
So a guy I know got a scooter recently. When he hits the throttle, the rpm's build up really slowly and when the clutch engages, after few seconds it goes flying. My friend told me he put harder springs, so the clutch engages on higher rpm's.

We came to a conclusion, it could be a clogged carburetor idle jet? It was sitting in the basement for 2 years.

Thank you.

 

Yeah sounds like something blocked....
What scooter is it.
Let me guess..
Speedfight?
Aerox?

 

If I remember correctly, it is a 1997 Gilera Runner. Definitely has it's signs of use.