Source for the Cup washers on the SU Air cleaner Wing Bolts

[Captain Obvious]

Coolness.

Since the only thing you're doing with the wing nut is locking it onto the stub of the bolt after you cut the head off, the threads there don't matter much. If I were doing that here, I would use imperial hardware. 5/16 (or 1/4 if I wanted a shoulder). I don't know if that makes your hardware choice any easier, but thought I would at least bring it up.

So the original wing bolt looks like it was made from multiple pieces as well? I've never thought about it and don't even have anything that runs carbs right now. But it looks like they did the same thing you are doing with multiple parts. Silver soldered together maybe? Or just a tight press fit (which I think would work great for you too).

Other input? You could chuck the hex coupler up in the lathe and taper the lead in hole for better target acquisition. It's not as big as the stock one, but you could provide some bevel there to help.

I'm still thinking about the other end that threads into the carb faces... Wondering if red Loctite would be good enough there instead of the thin jamb nut. That red stuff is pretty tough. I wouldn't be surprised if the bolt would twist off before the Loctite let go (cold).

You could cross drill, pin, and file flush. That would hide pretty well, especially if you're going to re-plate.

[zKars]

All good ideas. Sourcing the metric parts was easy, no need to bring any “outsiders” to the party.

The original wing bolt is definitely two pieces, no sign of any brazing or soldering, maybe just a tight fit. 

Red loctite might just do it. I’ll do one and see what kind of torque it can handle.I can’t use more than about three threads or I start taking up too much of the cavity for the wing bolt. 

TIG’ing that bolt in there is the hot tip (haha) but I need to practice. Best thing I got was a face shield with a magnifying lens. Old people....

[Captain Obvious]

Yeah, I figured on your side of the border, the metric stuff was easier to get. On my side, not unexpectedly, the inch stuff is easier.

I'm thinking that a press fit would be enough. I was looking at the original bolt in your fantastic pics and it looks like there's a small undercut on the shank end of the wing? Like they could have pressed the wing head on just a fraction of a mm further before it bottomed out?

If you think about the application, it's supposed to be finger tight. I'm thinking a nice aggressive "permanent" category press fit would be plenty. Use your hydraulic press to put it on. Just don't shoot the whole thing out of the press sideways into sensitive body parts.

9 minutes ago, zKars said:

TIG’ing that bolt in there is the hot tip (haha)

Haha! I see what you did there!

Any of that (silver braze, TIG) will ruin the plating and necessitate a re-plate.