would this reinforced motoforce crank be good enough for a stage6 racing 70cc cylinder? http://en.scooter-attack.com/shop/artikel.php?s=&artnr=MF30.16601&modell=20&l=navigation
should be, i'd suggest a crank with a bit more primary compresion though. (solid webs rather than cut outs) gives a better fuel/air charge into the cylinder.