The original fuel line for the flat head Tecumseh is braided 1/4" ID x 7/16" OD, not the "standard" braided 1/2" OD found at auto stores. There's a narrow passageway that the hose travels through from the gas tank to the carburetor. In a pinch I've used 1/2" hose but it's a tight fit and you have to work at it. I much prefer to use braided 7/16" OD hose which I get a mower shop. I'm writing this just after I put 1/4" ID x 1/2" OD in a 5 hp Tecumseh engine because, I had it on the shelf in a box, to cold to travel to the mower shop, too lazy to do it, mower shop that carries the hose is 10 miles away, it will be a long time before it gets changed, however, it is easier to change the carburetors to move the smaller 7/16" OD hose back in to the passageway slightly than the 1/2".