Im assuming that most of the 840cc rotax motors that are not pushing fully modded heads are in the mid 60s hp.
My brothers Tyrex 820cc motor built by himself and Dave Maxwell at 2x motorsports, Muzzy exhaust , AFE intake, Dasa intake mod, programable cdi by Dynatek and coils, Vforcejohn clutching, All perfectly tuned and runs on pump gas. It made 59hp on the Wellers dyno. and Jason Weller said his 840 was making 64hp. So maybe a full tilt high compression radical port job big valved, race gas only spining some higher rpms will see 70hp but I dont think there every day 840 will do 70hp. atleast thats what Jason told me.
2nd place is the first loser!!
Were a whole lot faster than you think you are.