Honda vario 2004 jerks problem

[cursedd]

dear,
I have honda vario 2004, when i drive on D and i push accelerator it gives me jerks. as if car is shifting down and gaining some rpm for better power.
but when i drive in S it runs pretty smooth and no jerks are felt.
Car rns completely on petrol.

how to resolve issue?
@Xulfiqar

[dayrider]

when was the last time you changed your gear oil?

[cursedd]

actually I have bought the car recently. so I don't know about it. will check the gear oil.

[dayrider]

get all oils, and filters replaced, and get all the rubber parts checked

[cursedd]

will do it and update here. thanks