Two throat woes

[DavidW]

Well it's been another one of those days. Complete clean up and rebuild of an old two throat for an ironhead chopper project. Everything was going great then went to unscrew the accelerator actuator linkage pivot and the little screw thread sheared. Anyone have a line on old parts out there?

[farmall]

That's easily repairable with an insert which would make it better than new. You can find inserts which install with standard taps to save $$. I'd insert both holes while I was at it. I suggest a tiny dab of anti-seize on the screws. Then they can be in there for decades and not pull the insert unintentionally.

Every carb screw I can replace with stainless socket heads gets it because corrosion sucks.The little "star" lock washers work best and are available in stainless. (S&S used slotted head screws out of either retardation or retarded tradition. I only like slots for adjustment screws so I can count turns easily.) I usually buy online.

Post your jet sizes etc when ya get it sorted. An Ironhead two throat thread would be kool because there's not a lot of info on them. I've never run one but I'm always curious.

BTW on small parts like that a conventional tap may be too long. It's easy to make a bottoming tap if ya prefer not to order one, bu the little ones are only a few dollars and it never hurts to have tiny threading tools on hand when ya fuck with carbs. Of course if you use a tap specific to the insert then you'll need to modify that. You could start the threads with an unmodded tap for convenience then mod it to bottom out. I strongly suggest using a drill press to hold your drill bit and taps square to the work. I'd drill a hunk of aluminum (easy to machine) and secure the part to it with screws. That really isn't much work and makes controlling parts easier.

https://www.practicalmachinist.com/vb/abrasive-machining/can-plug-tap-ground-down-bottoming-tap-262609/

Good video:

https://www.youtube.com/watch?v=2e7nc3Y5JzQ

[DavidW]

On a larger thread I would agree with the insert. However, best I can determine the thread has an OD of .110", the shoulder for the pivot is .158". After contemplating the design of the actuator as a whole (with the help of a cold beer) I believe S&S over-engineered it. They had a gasket on the cover and the pivot screw yet the actuator rod just had the usual bellows seal. And this is all on the "dry side" of the pump diaphragm. I think I'm going to drill out the thread and use a small Clevis pin with clips to repair it.

Otherwise its been fairly simple to rebuild considering the lack of parts suppliers. The accelerator pump parts and ball, main jets (52's), float needle and seat and various o-rings are all Super E. Float bowl and intake gaskets along with intermediate gaskets are available on line.

[farmall]

Ya can't lose that way and if it wears ya could bush it easily or use an insert if inclined.

BTW drills produce oval holes so if it turns out too loose ya can ream slightly larger, bush, or just use an insert.

All fit, bushing and thread info lives in this industry standard. Machinery's Handbook changes little so no need for the latest edition.

http://library.uc.edu.kh/userfiles/pdf/19.Machinery%27s%20handbook.pdf