wont go past 6000 RPM

[Shaun403]

My R50X runs great when on the stand revs up to 8000 rpm no problem,  however when i run the bike down the road past 6000rpm the scooter sort of dies drops revs as if it is blocked / clogged, when i rev it again it will go back up to 6000 rpm and if i hold it will keep going, however if i attempt to go past this rpm it drops in power

Any ideas?

Help appreciated

Regards

Shaun

[Shaun403]

I did change the variator pulley to this item on eBay could this be doing it?#320833316513, ?

[Shaun403]

What 70cc kits fit inc part numbers, and exhausts models etc