when i had vespas the acceptted cure for carboning up was block the small ens, pour a whole tub of caustic soda down the other end followed by a large amount of boiling water and stand ( well ) back, rinse and repeat until no more sh1t comes out, also handy for weed killing in the driveway ( not recommended doing this in the house, much jetting of filthy corrosive fluids all over the kitchen does not make you popular, not to mention losing the ability to breathe in enclosed spaces )