Bob cautioned me to watch the torque on the nut when installing them, as there was a fit up issue with them and he was working with Enya on it. When I got mine, I checked the nut against what I had in genuine OS spray bars and nuts, and I reported to him that the nut is too big on the ID. The spray bars were fine, and OS nuts fit them properly.
I just opened one of the ones I have and checked it for fit. The nut seems OK to me, it's looser than I would have made it, but its' also much deeper than those on the OS, so it has maybe 50% more threads engaged. I don't see a problem - these super-fine threads in brass are always a risk to strip out.
Limitations aside, these spraybars allow you to run your engine the way it was intended and to *not drill a hole in an unobtainable crankcase* that can't practically be restored without a machine shop.
In fact, some enterprising "engine person" might offer a set of machined collars that are the OD of an ST or other popular spraybars, and ID to pass the original part, and just long enough to fill up the hole in the case - that could then be JB-Weld'ed into the drilled-out holes to restore them. Operations are face off, bore to ID, machine OD, part off. ID ~3.52mm, OD .159 (for ST needle, presuming it was drilled using a #21 drill, which will leave sufficient clearance), and length about 2mm.
For extra credit, same thing, except part off long enough to go through the case and to the nominal-size venturi wall, then to be glued to the spraybar at each end, making a "dogbone" spraybar that takes up the extra space and will retain a
damaged drilled-out stock venturi. I have hacked together such things using K&S tubing and shim stock, but a machined part would be a lot better. The only reason the hacked system works is that the fit isn't very critical in that area,
Brett
p.s. I got out one of my Enya "identical" assemblies, and installed it. The threads are the same between the original OS and Enya copy. The seat seems to be deeper on the Enya assembly , but you can probably use the Enya needle in the OS spraybar, and probably vice-versa. The Enya spring is single-sided but seem to engage the ratchet better than the OS did on it's needle. Everything seems fine about the replacement, seems like it should work as well as the original, although I haven't run it or flown with it.
I guess I hadn't noticed before today, but the nut doesn't fit any nut driver or socket I have on either one, it's 5.5xx mm which is pretty close to 7/32, but that doesn't fit either. I don't recall having a special wrench in the box, so its some sort of "all 16ths" adjustable wrench, or, that horror of horrors, pliers.