The Rokons are "Love or Hate" bikes.
If you can set them up right and live with the weight and transmission quirks, you'll love them. Going fast has never been this easy. Many guys get on them and hate the lack of direct power transfer and engine braking.
The enduro models are well sorted, but I dunno about the MX ones....
Engines are plenty fast.
BTW, the pull starter on the Ebay bike needs to go back 90 degrees anti clockwise. Maybe that says a bit about the prep on the rest of the bike........
Regards
David