The carburetor needs tuning. It runs, but it bogs down under a load or quick acceleration.
The fuel accelerator pump is most likely bad and not pumping extra fuel during acceleration. The carburetor needs to be replaced or overhauled if you can find a mechanic with the experience to overhaul carburetors. I recommend having a mechanic, like one from YourMechanic, come and check the problem for you and provide you a diagnosis.
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