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Petcock..."corkscrew" spring

BigD_83

BigD_83

Forum Sage
Past Site Supporter
Inside the petcock, on the side with the plastic barrel that directs fuel flow, between that barrel and the metal post of the vacuum diaphragm:

there is a sprung clip, kind of "C" or "G" shaped with one part that points at the diaphragm.

Looks like this, except this one is mangled:




I have an old tank I borrowed while mine was being painted, and while working on it I think I tweaked the spring. It may have already been mangled as the petcock was frozen.

I've been looking for pics of it in position, with no luck so far. I know with some careful manipulation it can be bent back into the proper shape, as I did so with another one. However, I have a feeling it's not working quite properly, which tells me either it is not back in the right shape, or not in the right position.

Until recently, I thought that clip was just there to provide a stopping point for the petcock lever. Now I'm wondering, does the little bar inside the "barrel" push on the clip to press the diaphragm back into an open position relating to the PRIME position?


So, two questions:

1. Can anyone provide a photo of this clip inside a functional petcock, and

2. is there a source for these, other than another petcock?

I know the parts fiche does not show it, so smart money says no. However, there are other parts not listed in the fiches (choke assembly parts in particular) I know can be sourced.
 
Hopefully you are just curious and have no intention of rebuilding a petcock when new ( and functioning) ones can be had < $50 ! Anyways, I just opened up my old leakdownthevacline petcock; Yes, there is a metal clip/ tab that pushes out against the vac diaphragm WHEN the lever is in "PR" spot to let fuel flow. Looking at your pic, it seems that the "C" section of the clip rides on a taper - the clip doesn't rotate, it just advances towards diaphragm as lever is moved to "PR" spot.
 
I haven't bothered to look around for a new petcock yet, as it isn't my tank, but I feel like I should at least help the owner out, seeing as he was nice enough to loan me the tank and fender.

Funny thing, the metal on the inside mating surface of the petcock, where the mesh pre-filter sits, is very cheesy. If it were mine, I'd probably just source a new petcock.

Right now I'm mainly interested in what's going on inside, and how this spring works in conjunction with the plastic barrel inside the petcock, and I might just fritter away a little time trying to bend this thing back into form. It might work at best, and won't hurt to try.

Tom, I'm not sure I'm following what you mean by the "C" section riding on a taper...but I do get that the barrel pushes against the clip. I believe the bend in the "G" portion should point at/contact the central cylinder of the vacuum diaphragm.

It looks like there may already have been a rebuild once on this particular petcock, or at least the vacuum diaphragm looked very new to me. Of course, I think there was something like 5000 miles on the odometer, so it might have just looked new.
 
In your pic the "C" section is the undamaged section of the clip- it rides against the petcock knob on inside. The knob (on inside) apparently is a "ramp" so as you turn to "PR" spot the "C" section climbs the taper and pushes the end of clip (bent 90 degrees to "C" section) towards the center of petcock diaphragm to open it. The clip does not turn with petcock position , but it "wobbles" slighty as it moves out.
 
A truely brilliant and elegant design which unfortunately does not work very well.

Those always get bent wrong somehow.
 
tkent02 said:
A truely brilliant and elegant design which unfortunately does not work very well.

Those always get bent wrong somehow.
Click to expand...
Looking at mine, I can see that if diaphragm got gunked up solid (and couldn't move) and then if you moved petcock lever, it would likely bend clip. I sorta like the vacuum petcock.
 
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