Petcock - stuck in position

Ok so I removed the petcock from the tank, cleaned the mesh screen and dismantled the front of the the petcock.

It is the single vaccume style stock 78 KZ650 B style with the 2 phillips screws.

Anyways my question is this, When I removed the handle I found out what was wrong with it, the O ring had snapped and was binding the handle. I removed the old ring and replaced it with a new ring, put the housing back together and it moved freely.

The other day when I went for a ride I figured I was getting low on fuel, I went to switch it back to reserve and the handle was all bound up again, less that 2 days after I rebiult the thing.

Is there a type of grease or lubricant that I can use to keep this thing from locking in position that will not afffect the bike? I had only used WD40 to clean it and "lube" it, but I knw that it is not really a lub repacement, what shall I use for this purpose?

Kool Ryder

Maybe silicone grease, never tried it

I used a dab of motor oil (it's all I had at the time). Just don't use too much.