"For example a Doppler crank is designed to withstand the higher horsepower and higher RPM. So a stock crank will not hold up when matched to a 70cc kit."
hell naw if u keep it balanced and keep the bearings fresh the stock crank runs great and will hold the power, but yeah i see ur point. i had the stock one in mine for a long time no issue once i rebuilt and balanced the variator out
even the stock pulley will break down and the motor mounts will be destroyed in less than a year. lol.