RD 125 AS3/DX Power development/torque course

Hello municipality, I have brought a RD 125 AS3/DX back on the road. The engine has 12tkm.. new piston rings mounted, all seals and wedirings renewed, carburettor overhauled etc… On the roll the thing presses 14,5 hp at 8500 1/min at the crankshaft. however below 7000 1/m, in “goes” almost nothing. Light slope (2-3%) in the third gear 9501/min about 65 km/h => high and the speed drops to about 7500… then it loses slightly at speed … and if it is below 70 00 down is the oven off… Turn back again 9500, switch … the same game. I have already scratched at the front from 15 to 14 to 13… the transitions are a bit better… But the performance so blatantly drops does not go into my head… OK 125ccm is not much .. Does anyone have similar experience or a tip?