Are you saying you removed the air filter and kept riding it???
In your attempt to solve a (probably cheap) problem, you're inviting a whole host of others.
New belt and rollers, get yourself some.
Yeah dude, riding without an air filter is a very bad idea even for a little while.
These scoots don't need frequent maintenance, but they need regular maintenance if you want them to run well and last. Kymcos will go a very long while if you treat them well.
Agree with the other advice; Download an Agility service manual, follow the maintenance schedule and learn to do some of these basic things. I would also add to what others have put here that you should probably adjust your valves. You can find youtube videos as well as explanations here and in the service manual on how to do this.