Various factors affecting the occurrence of the Bridging of plug gap in 2 cycle farm engine were studied by inserting fine particles of iron metal into the cylinder, and the following results were obtained.
(1) The Bridging tends to occur easily when the size and the amount of particle increases and the spark gap is narrow.
(2) The difference of position of particles put on the piston head affects on the occurrence of the Bridging.
It increases on the side of scavenging port and does not occur on the side of exhaust port.
(3) The occurrence of the Bridge forming differs due to the place in the cylinder where adhesive substances as oil are adhered as the following order: electrodes of spark plug>cylinder head>piston head>non oiled into the cylinder.
(4) The length of reach of spark gap into the cylinder much more influences on the Bridge forming.
It increases at the other reach length except the fitted.
(5) Low-heat range of spark plug at the heavy load increases the Bridge forming.
(6) The Bridge forming due to the inserted particle is liable to occur at the side of light load and on the way of rising of cylinder temperature.
The warming up of engine is effective, while the cold starting is harmful for preventing the Bridge forming.
(7) Unfitted size of gasket induces many deposits of partcles which causes frequent Bridge formings for lasting period.