Swapped the 250 twin for a single in my 78 elan dlx, reused the carb from the twin (hr-172a) it starts easy and idles smooth, but it wont rev past 1/3 throttle. It's just enough for it to move but noe more. Plug is black and wet so it seems like the motor is flooding. My first thought was that the jet from the twin is to big, Main jet is 0.42 which is the stock jet from the twin, but according to the parts manual the single has a 0.46 jet which will only make it worse i presume. So, where do i start? Is this problem carb-related or are there other things that could couse theese symptoms?