with full power?
that can only happen if:
too much air
and too much fuel to match air ( carbs job is to match air with good fuel mix , that is it. think of it as EFI in a brick.LOL)
so close the butterfly plate more and make sure throttle cable is not sticking.
if you close the butterfly plate (AKA throttle stop screw)
and the RPM dont drop then you have an air leak. ( causes lean condtion )
but if you punched out the jets.
and are already rich.
then air leaks cause high RPM immediatly.
with full power, due to rich + extra air = perfect high rpm running. see? sorry algebra leak.
If already too rich, then any added air causes high RPM with FULL power.
and for sure the carb has lots of parts, that can go bad. (ive boiled out hundreds)
to me its a black box.
1: is the throttle jamming outside carb(box) Y/N
2: is the throttle plates jamming in carb , Y/N
3: are there air leaks below carb Y/N
if after doing above checks. no hits.?
then its carb rebuild time.
engine induction air leaks