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stock gas shut off valve

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harley44

Posts: 31

Joined: Thu Mar 11, 2004 1:01 am

Location: los Angeles., ca

Post Tue Jul 13, 2010 9:45 pm

stock gas shut off valve

I've looked thruogh the old posts, didn't find what I needed. I'm looking for a petcock (shut-off vave). my original thru tank valve is leaking slightly, enough to cause problems. I ride it several times a month, then it sits for a few months. I know the after market alignment tools need work. Can I take the valve apart and hand lap it? (eye ball alignment,mostly). and make it work or should I just put a valve in line. I am using an inline gas filter now. A little history.I'm riding a 1944 EL, I have owned it since 1979. rode for about two years. have a trophy from the dirt diggers motorcycle club, circa 1981 for a race at Ascot park in Gardena Ca. someone here was probably there. I then took it apart, found frame cracks etc. it sat in baskets for many years. My wife said "Just! put it back together" before the kids get out of highschool .Oh well I had to do what the wife wanted. I rode it again the day after my 50th birthday May 2005. now 5 years later I get to address some more issues. oil questions another post
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amklyde

Posts: 624

Joined: Fri Dec 19, 2003 1:01 am

Location: Wisconsin, USA

Post Wed Jul 14, 2010 7:25 am

Re: stock gas shut off valve

I removed the steel stem tip and replaced it with PEEK. Pressed the new material in at .004 and then just to be sure it would stay put, I cross drilled and pinned the insert with 16th" brass rod. So far so good. The peek is a little softer and more forgiving than the steel tip.
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harley44

Posts: 31

Joined: Thu Mar 11, 2004 1:01 am

Location: los Angeles., ca

Post Wed Jul 14, 2010 7:59 pm

Re: stock gas shut off valve

thanks, amklyde, I'm not a machinist. That might be a little ouy of my league. Is PEEK similar to JB Weld? I've heard of it before, but not sure what it is or does. Is it moldable at a certian setup point?
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Frankenstein

User avatar

Posts: 1544

Joined: Thu Jun 27, 2002 12:01 am

Location: Interlaken, NY USA

Post Fri Jul 16, 2010 8:15 am

Re: stock gas shut off valve

The old tried and true fix is to press off the threaded portion on the rod, it's splined. Then use cigar ash as a lapping compound to do the final lap in of the tip in the valve seat. Cigarette ash is too coarse, as I understand it. ( I don't think it needs to be a Havana, by the way). I've used it on the earlier brass petcocks on Knuck/flathead tanks to some sucess.
DD
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harley44

Posts: 31

Joined: Thu Mar 11, 2004 1:01 am

Location: los Angeles., ca

Post Thu Sep 09, 2010 9:46 pm

Re: stock gas shut off valve

I bought a replacement thru a local shop. I put it in blindly. It leaked like a stuck pig!! Upon inspection the seat looked like it was grooved vertically every 90 degrees. perhaps waiting for someone to machine it its mating part. oops, I'm not a machinest. I tried my original seat, the part at the bottom of the tank, and the new shaft, that almost worked. still a little bit of seeping gas. I think I will now try lapping the 2 best parts as suggested by earlier posts. thanks everyone for your help. any other ideas are welcome.
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TOMYKA1951

Posts: 7

Joined: Sun Aug 15, 2010 12:40 am

Post Sat Sep 18, 2010 10:10 pm

Re: stock gas shut off valve

My stock gas tanks didnt have the valve assembly and the guy who helped me build my knuc had the factory aligment tool he checked the tank and it didnt need any thing. however my after market valve assembly did require my lapping
it in some before a good seal was there. i used automotive valve grinding paste. low presure full turns then back , wash out and look for clean shinnie mateing ring on seat and rod.
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Cotten

User avatar

Posts: 2671

Joined: Thu Sep 30, 1999 12:01 am

Location: Central Illinois, USA

Post Sun Sep 19, 2010 8:32 am

Re: stock gas shut off valve

I was under the impression that the threaded portion of the shut-off rod must be removed for proper lapping.

After several unsatisfactory attempts, I found that the most leakage was indeed a problem of alignment.
But the factory alignment tool has a serious flaw: metal must be bent passed true so that it can relax back to true, and smacking the tool with a hammer just doesn't cut it!

So I machined a tapered tap for the threaded bung, and drilled and honed the center for a ground 1/4" pilot rod:
PETALIGN.jpg

Just looking through the hole gives a great indication of mis-alignment.

The pipe to the left in the picture has a top cap brazed into it. This can be used to massage the top of the tank when necessary, and the long tap at the bottom can be used to force the bottom straight as well, until the pilot rod slips through smoothly.

But even with a lapped and aligned petcock, I have alwasy relied upon a pair of pliers ground to safely clear the paint to snug things up if the machine was to sit for an extended period of time.

....Cotten
PS: Thanks Kyle!
Now I have one more item to use to whittle down my hoard of PEEK scrap!
PhenylEthylEthylKetone is the greatest stuff invented since flaked flint.
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dougspair

Posts: 5

Joined: Tue Jun 21, 2005 12:01 am

Location: Sacramento, Ca...USA

Post Wed Oct 20, 2010 2:29 am

Re: stock gas shut off valve

....Knuckle fuel tank valve. I have the original thru tank deal...lapped the valve/seat with fine grade Clover compound....works fine....bike goes 1/2 block if I forget to open the valve...doesn't seep at all...
The question about PEEK...that's type of hard plastic that must be machined....but has abit of 'forgiveness ....might be good for valve...
Tapered seat with 4 vertical lines at 90 degrees?...sounds like someone tried to cut seat with 4 flute tool and didn't allow tool to float a little at end of cutting...I've seen this type of stuff before...

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