How To: machining Schebler float screws
Here is another quick How To article from this week’s wrenching sessions.
The Schebler carb was used on the majority of American motorcycles during the 19teens and twenties, my X has a 1” model H. The float pivot is a simple pin that fits into small holes that are drilled into the ends of two 1/4-28 screws. One of my screws had fallen out of the carb, so I bought a box of screws from McMaster Carr and did a little lathe work to replicate the missing screw.
The hardest part was how to grab the little buggers while cutting them. I made a workholding fixture from a piece of round steel, with a 1/4-28 threaded hole in it. First that allowed me to cut the heads of the screws to be smaller.
Then the screws were screwed into the back of the fixture, so that the threaded ends were sticking out. I could then part the screws off to be the correct length, and also drill the small hole for the pivot pin. I only needed one part, but since none of the shops that supply Schebler replacement parts sell them, I went ahead and made a few extras.
Top, standard screw from McMaster Carr
Middle, head diameter turned down
Bottom, original Schebler screw and pin
Here is the fixture in the lathe.
On the left is the fixture with a screw installed. I’ve cut it roughly to length with a saw, now it is ready to be faced off and the small hole drilled.