Looks like your mixer has had the nipple broken off and a repair made by inserting a section of pipe for the fuel line nut to hang onto. Your mixer nipple should look more like Jim’s. If your mixer body is aluminum, it would explain the breakage, and also leaves you fewer options.

BUT – if its bronze that is painted over, you have the option of silver-soldering a new nipple onto the mixer, then you can use a proper compression nut and sleeve on your fuel pipe, and that should solve the leakage issue.

Oil groove in bearing – Not saying its the "best" way to do it – its just the way I do it, cuz I don’t know any better – but my low-precision method to make spiral grooves on the ID of bronze bearings is by using a carbide boring bar and making one heavy cut that covers the majority (maximum 2/3, but a little less will do) of the length of the bearing. I make the cut with the lathe in its lowest back gear speed, and make the cut by withdrawing the bit OUT of the part. You don’t need to make a groove that is 60 thou deep, you’re just making a channel for the oil to get in and do its job. I start by moving the tool bit in to the desired position, then advance the tool into the work the desired depth (I like 0.020" myself) while rotating the spindle by hand and do about 5-6 revolutions right there. The lathe is then turned on while the tool is withdrawn from the bore very quickly (less than a second), and it gives a nice even spiral all the way out. This method does raise a burr at the edges of the groove, so it involves a bit of refinishing work to get the burrs off, but finger sanding usually does it real fast.

transversely, you don’t really need to make a spiral groove, you could get away with a straight one.

Hope it helps.

Best,
PM T2