Two words: No Suspension. This is a utility vehicle for very slow riding. Rokon did make an enduro/mx bike in the early 70s. 340cc sachs snowmobile engine, salisbury variable snowmobile type transmission. Very innovative at the time- had cast magnesium wheels and disc brakes among other things.
Achilles heels: Pull starter made it tricky to start safely, as there was no neutral in the driveline. When it revved up, it took off. If the pull starter got any dirt or mud in it, it would not engage. The variable pulley belt system could not be sealed due to heat buildup, so when it got wet, it slipped- badly. That also let dirt and mud into the variable pulley mechanism, which wore out components very quickly.
Norm Kern