The burners have a screw holding the top on, you can see it if you look from under the grill. You will need a stubby screw driver to undo the screw and the burner will lift off so you can clean the jets. But be very careful as you lift the burner off as there is a very fragile asbestos gasket underneath and it might break - no idea where you would get a new one. It would probably be better if you took a thin piece of wire and poked it carefully down the burner grooves so you don't disturb the asbestos gasket.