This youtube vid shows a Yingang motorcycle reaching 160kmh on the speedo in no time! I read up on the speedo errors, and you're probably right, it'll be closer to 80MPH than 100MPH.

Still, Yingang engines are rated 26HP, compared to the sub 18HP for most other chinese engines.
I've read some ridiculous claims of a guy saying he got near to 40HP out of his engine,
I think it's to be taken with a grain of salt, but removing the rev limiter from 8,5k RPM to 11.5k rpm should theoretically raise HP from 26 to 31+ HP.
And improving airflow, by putting a larger air filter, could raise it by another 2HP, increasing a total of 7HP at full throttle. Combined with the higher RPM, I believe they could surpass the 95MPH barrier, perhaps even go 100MPH.

I'm just writing from what I read up on online; but the results are much better than the Roketa or other chinese bike, that already has an unrestricted air intake.