could be a rusty gas tank mixed with dirty carb or an air leak. The bogging shows signs of dirty carb or air leak while the dying engine seems like crap is getting in your carb- I.E. dirty/ rusty gas tank-
1st. Clean the carb very well --then reinstall and while it is idling spray carb cleaner at various points around the carb and intake- if it kills the engine you have an air leak. If so, use RTV gasket red sealer from Napa or auto zone and seal up where it leaks.
Also, for the tank I would install in inline fuel filter from auto zone- costs 2.50. it is easy as pie to install and will prevent most light rust/dirt from your tank from clogging your main jet in the carb.
If it still bogs you most likely are running a too large main jet (brass screw in carb) and you need to down jet. its a dellort 14.12 on a V1 right? good news is 1977mopeds has all ranges of dellorto jets for you. Though my bet is on 1 and 2.
Good luck- i dont think it is the condenser personally. nor a soft sieze. 1 and 2 are the most common issues.