When is a petcock not leaking?

[Incubus]

It seems like a simple question. And I am pretty simple, so it fits. But maybe not so.

I've been futzing with my petcocks for, like, ever. They were leaking and leaving pools of gas under my bike. I know, better than in the oil, but still not a recipe for domestic tranquility, what with the fumes drifting into the house. I've replaced the gaskets and bent the washers, like the tech tip says to do. I've had the tank off the bike for a couple days with fuel lines attached the the petcocks to see if the leaking has stopped. It almost has.

Overnight I will get a trickle of gas collecting in the looped fuel lines. Is this the closest I can expect to sealing these suckers off? Are the needle valves supposed to stop the rest? I hate trusting needle valves. They lure you into a sense of complacency and then stab you in the back.

I really wish these had a shut off.

Patrick

[Ken Talbot]

When they work properly, they will completely shut off the gas flow - no dribbling, no slow pooling, etc. When you were in there, did you check out the spooge hole? Yes, there is a small orifice in the body of the petcock that needs to be cleaned out also. Read about it here
http://www.xs11.com/forum/showthread...petcock+spooge . If this hole is plugged, the vacuum is not released, so the diaphragm is held open, and you get a leak.

[strom]

mine leaks/leaked thru the spooge hole.... the little bastard!

LP

[mro]

Have GAS.........???

My daily ride (80G) with stock petcocks don't leak at all (as of checking em last June)

There are kits to replace internals for stock petcocks and after market manual petcocks (on/off, not vacuum actuated)

http://www.z1enterprises.com/SearchR...tcock%20repair

Think MikesXS.com has either parts or after market petcocks too.
May be cheeper???

Good read about old petcocks here:
http://www.z1enterprises.com/reference/petcock.aspx


mro

[skids]

I see you has a 79 xs11. If she is a standard, I would recommend the following. The diaphragm operates under vacuum to pull a plunger and open the flow of gasoline. If you have not yet been into this area already, you will discover an o-ring around the plunger. When there is no vacuum, this o-ring makes a seal by pressing the o-ring againg a conical seating area. I recommend that the O-ring be replaced and the conical seating area be polished. I wouldn't stretch that spring, because I tried that to force a better seal, and then I had fuel delivery problems when the bike was doing 70mph.

[Goin Commando]

https://www.partsnmore.com/cat_index...&category=carb

Look at the bottom of this page, might be something to consider.
No more vacuum, one less problem to worry about. Just gotta remember to shut them off at the end of your ride. The prices are very resonable.

[Goin Commando]

From Parts n More:
PETCOCK ADAPTER PLATE - 46mm
Fits: XS1100 (78-81) Standard model.
46mm Adapter Plate - 46mm (1.811") center to center mounting holes.
Use this plate to adapt our Universal Fuel Tap 3/8"NPT petcock part # 20-0100 to fuel tanks with 46mm (1.811") center to center mounting holes.
some slight modification maybe be required to enlarge tank opening as petcock will protrude through adapter plate about an eighth of an inch when tightened in place.


$6.00US EA.

Part#20-0103

[Incubus]

Yeah, I should have gone that route, Commando. Instead I bought the PNM petcock rebuilt kits. I like to go stock when I can.

So, since the rebuild kits come with a new diaphram with a new spooge hole, I don't think that is the issue. There also hasn't been any vacuum on these since the rebuild. Just sitting on the bench waiting to not leak. The petcocks are sitting in run position with less than a gallon of gas in them, so it should not be an issue with the o-ring on the vacuum plug because there shouldn't be any fuel getting into the main fuel draw pipe. Pardon my technical terms, but I don't know the proper name for these things. The hole where the vacuum plug fits has been cleaned with lithium soap grease and a q-tip and looked real smooth. But I figure the dribble must be coming from the main rubber gasket.

Anyway, I pulled the plates off the face plates and bent the washers some more to put more pressure on the plate. I hope that works.

Patrick

[Goin Commando]

A peice of wet-or-dry sand paper (about 400 grit) laying on a peice of glass plate and some WD40 sprayed on it makes a nice place to resurface flat parts. Take your lever/valve back out and resurface the part that goes against the round rubber with the 4 holes in it. This should help. You could also do this to the other parts that hold the diaphram. I like the idea of polishing the hole where the plunger/o-ring goes also, because the gas has to leak from there first to get to the round rubber with the 4 holes in it(unless it is leaking past the prime hole).
But I would try streching the spring a little bit, but not so much as to cause problems when the vacuum is at it's lowest in the intake. Just like the springs in your forks they tend to "sack" over time and with use also.
Good luck

[Ken Talbot]

Patrick, the spooge hole is not in the diaphragm. It is in the outer half of the petcock body, the piece that you remove to get at the diaphragm.

[HobbyMan]

Mine used to leak like that. I finally just got all new seals and a vacuum rebuild kit. They havn't leaked since. Also, the gasket beween the tank and petcock must be replaced if it is old. I tried at first to reaseal it with a number of different compounds, nothing worked. Why isn't there an OEM part number for petcock rebuild kits? If gas is leaking out through the carbs and airbox, you should just need to replace the o-ring on the diaphram and the seal beneath the lever. If it is leaking directly to the outside and dripping off the petcock, the seal between the tank and the gaskett on the bottom of the petcock need to be replaced. "Nothing is sure but death and taxes," and sometimes a leaky petcock.

[motoman]

If you all are buying the petcock kits, your gonna create yourself unending problems. If your diaphrams don't have any holes, clean everything real well, polish the seat, DO stretch the spring ever so little, can use same O-ring, put it all back together using dialectic lube on O-ring, and diaphram as a seal, Mines some 25yrs.old, and both were leaking, even while running, so did the above without replacing anything.............been over a year, and not even a sniff of fuel.............after doing all that and they still seep a bit, remove them from tank, dissassemble, and stretch the spring ever so little more............it'll work, been there done that.

[Brian_D]

Patrick,

Did the left and right-side lever and lever plate swap from this thread not work?

[Incubus]

I looked at that Brian, but I don't think it would do me any good, so I didn't try it. From what I've read on this forum and from what I saw in my own petcocks, most of the leaking seems to be around the gasket behind the selector, not from the plug that the vacuum diaphram operates. Switching the parts around to create an "off" position would solve a leak caused by a problem with the vacuum, but it doesn't appear that it would do a thing about a leak caused by the rubber gasket behind the selector.

In my case the vacuum may or may not be a problem. Until I've solved the leak from the gasket the diaphram is irrelevant.

Patrick