Leaking gas

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longhorn
Posts: 61
Joined: Sun Jul 15, 2007 11:58 am
Bikes: 58 servi-car
64 panhead
65 panhead
70 shovel
Location: SE Minnesota

Leaking gas

#1

Post by longhorn » Tue Apr 24, 2007 10:18 am

My newly acquired 65 is leaking gas, all over the place! I have rebuilt the Linkert, squaring up all surfaces, new gaskets, float,needle, and seat, etc. I have also discovered that the fuel shut-off is not sealing tight, small drip, but steady. I have taken this apart, can see no problem's, screw's tight, but will not seal-up. I don't like it, at all. Gas is leaking out of the fuel shut off, down the fuel line, through the needle, and seat, out through the head gaskets. First off, how do I seal up the fuel tank shutoff? Why does the needle, and seat, not hold the fuel back? Now that the gas has leaked into the cylinders, and out through the head gaskets, I'm thinking that some of the gas has bypassed the rings, and is now in my oil, what should a guy do? Help! Jim



King
Posts: 387
Joined: Fri Apr 02, 2004 5:05 pm

Re: Leaking gas

#2

Post by King » Tue Apr 24, 2007 9:13 pm

Jim

Fairly common Panhead problem.
Over time the shut-off seat and rod get worn, and no longer seat properly. This puts gas under gravity pressure in your line and causes the rest of the mess you described. It is possible to refurbish them but it takes a special tool ($$) to do the job. My solution was installing a simple plastic twist shut-off from a lawn tractor. Of course you have to have a section of rubber hose in your line to do this, mine is just below the carb.
Another source of leakage, and it sounds like you probably have that also as you describe gas dripping off the line, is from around the banjo fitting below the left tank that connects the right tank to the left. The gaskets above and below the banjo give out and a persistent leak occurs. The best remedy to this is to get two Linkert bowl nut gaskets (OEM 27376-2 to replace the brass ones that are standard. The bowl nut gaskets are crushable copper and do a better job of conforming just don't tighten them too tight.
A third source is the rubber packer (OEM 62094-40) that goes over the fuel line where it enters the bottom of the shut-off valve/banjo assembly and is compressed by the packer nut. This rubber packer will get hard over the years and no longer seal the line.
So I would drain the tank and replace the gaskets and packer for a start. Then either install a separate shut-off or replace the stock one, repos are available but I don't have any experience with them. Maybe someone else can steer you on to a good one.
Your description of gas coming out of the head gasket is a matter of some concern. First it must mean your gaskets are leaking. And if gas is coming out of the head gaskets I would think that gas is getting into the crank. I wouldn't attempt to start the bike until all of this is resolved as having gas in the crank is not good and will need to be purged before starting.

Good luck

King

panz4ever
Posts: 521
Joined: Fri Aug 12, 2005 5:45 pm

Re: Leaking gas

#3

Post by panz4ever » Wed Apr 25, 2007 3:35 am

longhorn, my 65 initially would not seal at the gas shut off rod position. Rather than modify a stock set up I used valve lapping compound to ensure the shut-off rod and seat are mated properly. Took a little time to get it right but haven't had a problem with it in the 37 years I have owned it.
King is dead on about replacing the brass with copper crush gasket. That has worked very well for me as well.

Cotten
Posts: 6911
Joined: Mon Aug 26, 2002 9:09 am
Location: Central Illinois

Re: Leaking gas

#4

Post by Cotten » Wed Apr 25, 2007 2:57 pm

The 5-gallon tanks with the rod-style petcock were one-year-only for a good reason:
The expanded tanks proved flimsy enough that even over-torquing the banjo fitting could distort the tank, and mis-align the seat with the rod.
The Factory tool for aligning the top and bottom of the tanks was a feeble and flawed attempt, as metal must be moved past 'true' before it will spring back to 'true'. Since it is a simple screwpress, it can only approach 'true'.
It is easiest to straighten the bottom bung by threading in the empty seat, and using it to visually inspect its alignment with the top hole. Then a piece of pipe over it, or a few taps with a soft mallet, will allow it to be tweaked in the direction it needs to go.
Leakage at the carb focuses upon the floatvalve, however other hardware can affect it.
If its a rubber-tip needle, replace it with a monel needle that fits.
If you can detect wear upon the pivot pin, replace it.
If the new pin still has slop within the lever, replace the lever, too.
If you can detect leakage through the valve by sucking upon it, try "setting" the needle into its seat by placing the valve nipple-down on the benchtop and lightly smacking the needle with a wooden screwdriver handle, or something similar.
The bowl mechanism is very much like a toilet.
If the float is not buoyant enough, the valve will keep "running", just like a toilet.

....Cotten

longhorn
Posts: 61
Joined: Sun Jul 15, 2007 11:58 am
Bikes: 58 servi-car
64 panhead
65 panhead
70 shovel
Location: SE Minnesota

Re: Leaking gas

#5

Post by longhorn » Fri Apr 27, 2007 2:51 am

Well , I think she's sealed up. First off I took Panzr4ever's advice, and lapped the shaft, and seat. Then I noticed that the threaded portion of the shaft, was not seated to the top of the knurling. I tapped it tight to the knurling, now the threaded portion does not bottom out against the brass insert, before the shaft bottoms out. Seems to be holding gas. Still have the problem of gas leaking through the brand new needle, and seat, that I got from V-Twin. Any suggestions on where to get a good needle, and seat? Thanks Jim

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