New scooter grind sound

[Mpell]

New scooter 49cc Yiben
1500 miles
Done all the oil changes at 600 miles
Changed the gear oil
Filter is clean enough

It was working perfect till a few days ago. Before getting to full speed a pulsating grind sound that vibrates the floor board starts and it feels as if it's held down. At slower speed it is smooth. Only when I go full throttle it does the vibrating noise.


From what I've read in other threads it seems to be the gearbox cap bearings. Could it be anything else?

I found 150cc caps with bearings in amazon but I'm not sure if it would be the same fit.

I don't want to take it apart if I don't have to.