gggGary, nice expo on petcocks. Since becoming a 78 SX650SE rider in 82, I've had good luck using most of the procedures you displayed and you had a few new tips I hadn't considered yet (ex: didn't have a Dremel last time, but will next!). I've had good luck with the rebuild kits 2 times now. Over the years I've successfully used spray silcone, silicone plumber's grease or Amsoil synthetic bearing grease to sparingly lube the various rubber gaskets and anything that would rub them when assembled. The spray is easier but doesn't last. In any case I consider lubing to be essential for longer life of the petcocks and gives me fighting chance to reuse parts likely unavailable in the field.
The comment to use Marvel Mystery Oil to help here is spot on, though I didn't consider it for that reason back in 85 when I started using it often. My main excuses are it's really good at keeping chambers, valves and sparkers clean of carbon. It helps carbs moving parts and resists rust and corrosion anywhere in the fuel system... my tank doesn't rust despite long periods of inaction. The insides of exhaust pipes (and hence mufflers) are gray too. In cars I usually get a few more MPG and always have it in the tank for emissions tests (esp older cars). And oooohhh, that lovely scent of sweetened ATF!!!
I don't condone thread wrap in petcocks. Micro-bits tend to shed on assembly or from vibration (and twins vibe, man). Much prefer to use Permatex Gray gasket sealer/maker (carefully applied) on the big petcock to tank screws. For them I use it on the screw threads where they will clinch in the tank threads and just under the screw heads where they will seal against the petcock body. I use Gray on the petcock gasket area where it will seal to the tank. The vacuum barb threads are a good spot, too.
In all cases, let all dry overnight to be inert to fuel. This has been very reliable stopping leaks in these areas. A couple times I've had to pull the petcocks on the road some time after a rebuild (see below) and the Gray often comes off clean enough to be reused if the tank paint was good and clean when sealer was installed. A few other reasons: it's easy to remove next rebuild, acts both as a thread lube and a screw retainer, and it's good at protecting threads against all evils.
One thing that I learned was to use the later 79 model petcock gas filters. One reason I had to repull the petcocks was the OEM 78 filters are in 2 pieces. A couple times, the top part detached in the tank and I had to retrieve and replace it. Happily discovering the 79's were one piece was an easy fix. Never use the 2 piece OEM filters!!
