If it idles and wont rev up you need to check a few things.
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Make sure the fuel line has no leaks and the primer bulb is pumping up hard.
Make sure the fuel tank is vented.
Check/replace the fuel pump diaphram.
If the motor sat a long time you could need to have the carbs rebuilt... idling
with no power is usually a sign the carbs are gummed up and will have to be
The seal is fairly easy if you know what your doing... get a service manual.