Problems with my Kymco Agility 50'

[BossHogg]

Hey guys, I do have a problem with my scooter.
It's a Kimby Agility 50 '16 wheels.
Today I have rode some kilometres and nothing was wrong, untill when I pull the throttle to accelerate, it doesn't go harder than 10km/u. It's like that I feel the engine is forcing to go faster but it simply cant.
I'm not experienced in scooters and such so I'd appreciate some help from anyone who might know what I be having here.

 

[Lodewijk]

Are you Dutch? Maak dan gebruik van de Nederlandse gedeelten van het forum svp. If not then hope someone will come to the rescue soon