I have only owned/still own the china ht engines. I started off with a road bike with a 66cc and a 36 tooth rear cog, absolutely no torque but heaps of speed (79km/h)
Right now I have a stock 66cc, which has been balanced, on a K mart bike. It runs so smooth.
soon, mabee in 3 weeks I will have one of sportscarpats boardtrack frames, it will be number 2.