I've not yet had the petcock apart on my bike (see signature).
However, a while back, I developed what appeared to be a diaphragm leak that was letting gas into the petcock vacuum line, thus making the bike run rich intermittently. Luckily, Serowbot diagnosed that one for me.
Well, I then disconnected the vacuum line from the petcock, plugged the vacuum port at the petcock and then plugged the top part of the vacuum line. The bike's been running great ever since.
When I shut the engine off, I position the petcock to ON. Before I start the engine, I position the petcock to PRI. I realize that I'm essentially running on RES at all times, but I want to emphasize two things: This is not a problem for me, the way I ride the bike, and I do not consider having to reposition the petcock all the time an inconvenience. As an old-school biker, this is "normal ops" for me. As a matter of fact, I find myself wanting the shut my Gold Wing's non-existent petcock off when I shut the engine down on that bike.....and it has fuel injection!
Are you still with me? Here's my question:I realize I should either do the manual petcock mod, or buy a new petcock. However, is there any way the petcock could leak gas into the petcock fuel line when the petcock is set to ON and there is no vacuum being applied to the petcock vacuum port?
If gas can't leak out under those conditions, I see no need to do the manual petcock mod. I can happily continue on doing what I'm doing (remember, having a RES capability is not important to me). However, like I said earlier, I have no way of knowing this as I've never had one of these petcocks apart.
I do, however, plan to remove the petcock vacuum line altogether and plug the intake manifold vacuum port itself.
TIA!