If no improvement after carb thorough clean (or even before), with the choke on idling suggest spray a broad spray of starter aerosol at carb area, if it revs higher change the spray nozzle to to a fine tub, spray check the carb lid & where the throttle cable enters are sealing properly, check the idle mix & airscrew, direct spray the rubber intake manifold to check for perishing/leakage. A spray can in wide spray mode can identify there's a leakage issue & then with that fine tube you can identify what's leaking. Leaks so mess with idle !
If all good next check is compression through ring wear, also remove the baffle temporarily and see if it idles any better ... the oil & carbon can choke up the baffles in the oem exhaust, pipe may need a thorough clean out.
PS Always loved these bikes, was like an xr75 but a 2 stroke powerhouse. Imagine retrofitting a good pipe, reed valves, pinch all the technology that Honda through into the 50cc road racing class or incorporate some of the best mods for the Honda Express SR 50cc two stroke motor.
