If the carburetor is already off the lawnmower, then you should spray the outside, remove and clean the bowl, clean the float and any passageways you can see, reassemble, reattach, and spray passed the butterfly (while running) several times. If the carburetor is still on, then start mower and spray passed the butterfly several times. Be careful not to get any overspray on the paint or on plastic covers/housings.