petcock diaphragm care?

[Dostoy320]

Maybe this is a dumb question... Gonna ask anyway.

I had to rebuild the vacuum-actuated petcock on my GS450E this spring because the ON/Reserve lever was so gummed up it wouldn't move.

The vacuum shutoff valve has been working fine on this bike, but I thought as long as I was in there I would replace the diaphragm with one from a rebuild kit so I didn't have to worry about it failing on a ride. Long story short, after several wrong orders, I gave up trying to find a kit that fits my petcock, and I've also read on this forum that some of the kits are junk anyway.

So my question is: Is there anything I can "treat" the diaphragm with before closing things back up? What is that thing made out of anyway? Some sort of rubber? Will anything applied to the "dry" side of the diaphragm help to keep it supple going forward?

[Gorminrider]

yes, I've had that problem too, looking for the correct diaphragm for an "E" type petcock. Does yours have a slightly larger diaphragm than the one they sent you? Does your outlet face forward versus the rear facing one that interferes with the frame and seems to be the replacement for the original part number? * (see below) Do you have a screw type "Prime"?

So my question is: Is there anything I can "treat" the diaphragm with before closing things back up? What is that thing made out of anyway? Some sort of rubber? Will anything applied to the "dry" side of the diaphragm help to keep it supple going forward?

I'm guessing it's a viton-type rubber adhering to the fabric. Probably nothing will help it because gasoline will wash anything applied off the inner side. Keeping it in the dark inside a petcock that has fresh fumes is probably the best thing you can do...ie: run/ride the bike, fresh gas, stabilizer... Some of my petcocks work just fine after 35 years on a bike that has been somewhat taken care of and used a bit at least seasonally.
But on my worst one (the hard one to find and replace -like yours?) I went so far as to take a diaghragm out of a propane regulator and using it...re-attaching the o-ringed plunger carefully..."amazing" that it almost works (ok on a Prime setting though and that's something useful in the interim) ... a bit too thick? and not quite large enough to trim into the size of the original...

I'm Still watching out of the corner of my eye for a source of the same viton-fabric sheet the petcocks use....

* The Error replacement can be modified apparently..Argongas(sp?) here pointed out you could drill and insert an outlet to face the correct direction.

[Dostoy320]

yes, I've had that problem too, looking for the correct diaphragm for an "E" type petcock. Does yours have a slightly larger diaphragm than the one they sent you? Does your outlet face forward versus the rear facing one that interferes with the frame and seems to be the replacement for the original part number? * (see below) Do you have a screw type "Prime"?

Yes and yes! Kit diaphragm too small... All aftermarket or OEM petcocks I find online have rear-ward facing fuel and vac ports that wouldn't work with the E...

I guess I'll put it back together carefully and hope for the best.

Am I correct in thinking that if the diaphragm failed while out on the road, I could turn the prime screw and ride it that way to get home?

[Gorminrider]

Sure. just turn prime screw back to in when you park the bike... and (blahblahblah) this assumes your float needles are working ok

....by the way- just mentioning off the cuff- I think a kind of vapour lock in the fuel line can be a nuisance per a diaphragm tap if the fuel line is not direct before it goes down to carbs...not quite sure what I'm talking about here except pertaining to the work-around of the fuel hose using the WrongTap (you and I at least understand )but maybe someone else has seen it with clear fuel lines...a bubble in warm weather.