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stopping a leaky fuel tap

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stopping a leaky fuel tap

Post by callum12 on Thu Apr 24 2014, 22:43

hi all,
has any one got any tip to stoping a leaking fuel tap on a lister d? it leaks from around the tapered valve bit so it was recommended to be to try some valve grinding paste and take out the brass bit that stops the valve from spinning all the way round and grinding it in. then clean it REALLY well as not to grind your carb and engine. this has helped a lot and now its more of a weep but I'm still worried my engine will spontaneously combust! (and not where it should be doing so Laughing  Laughing  )
thanks all,

callum

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Re: stopping a leaky fuel tap

Post by Rob bambi on Thu Jul 03 2014, 20:50

Hi mate in side yo have a bit the truns or pulles out/in the tap which has a weird gasket papery stuf round it that seals is if you put the plumbing stuff roumd migjt work?

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Re: stopping a leaky fuel tap

Post by callum12 on Thu Jul 03 2014, 22:33

i think you mean the cork stopper? my tap has no gaskets at all. it has a tapered brass section with a hole though it, when you turn the tap to the on position the handle turns the brass tapper so the hole lines up with the hole straight through the body of the tap. the tapered valve bit is held in with a spring and split pin.
the plumbing stuff you mention it most likely PTFE thread tape? that might work once or twice, but it would be "mushed up" by the tap being turned on and off. I have got a spare tap that i haven't tried so i'll give that a go.
thanks,
Callum

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Re: stopping a leaky fuel tap

Post by Rob bambi on Fri Jul 04 2014, 06:00

Yh if you had the push pull it might of worked but yh i wouldrnt have a clue about that one

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Re: stopping a leaky fuel tap

Post by Darryl Ovens on Fri Jul 11 2014, 22:56

Yes I tried lapping the taper on a couple of leaky taps too, same as you, it reduced the leak to a weep.  I think the problem is that it laps it ok but the taper is not quite in the same position by the thickness of the abrasive particles.  This means that when it is clean, (ie no abrasive), the taper goes, (or needs to go), slightly further in and now it no longer fits 100% which it has to if it is going to seal.  My feeling is that finer abrasives will make it better but take much longer and never quite "get there".  
I have wondered if there is a tiny ridge that was outside the body while lapping, that now prevents the male taper sliding in that little bit more.  Haven't thought of a way to remove it, (short of judicious filing with a jewelers file), so haven't tried that yet.
Anyone got any other ideas?

Cheers
Darryl

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Re: stopping a leaky fuel tap

Post by callum12 on Fri Jul 11 2014, 23:01

thats a good point, i'll check mine for the ridge on the male tapper you mention.
i have a lathe so i might be able to sort something to remove it.
thanks for that Darryl,

Callum

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Re: stopping a leaky fuel tap

Post by Darryl Ovens on Sat Jul 12 2014, 05:37

Replied an hour or two ago, don't know where it went?

I suspect the "ridge" if it exists, may be too small to see.  
And also suspect it may be a challenge to get the male part true enough in a lathe to remove only the ridge.  Wink

Thats why I was thinking gentle rub around with a jewellers file, it will follow the surface.
Alternatively maybe scrape around the large end corner just enough to break the corner where the ridge would hit. 
Have yet to try it though.

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Re: stopping a leaky fuel tap

Post by matt86 on Mon Jul 14 2014, 17:46

lap the tap in with some brasso t cut or if quite pitted or ridged use some valve grinding paste .


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Re: stopping a leaky fuel tap

Post by callum12 on Mon Jul 14 2014, 22:09

done all that, it's as smooth as anything. i'll give is another go though, as well as the ridge that Darryl suggested.
thanks
Callum

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Re: stopping a leaky fuel tap

Post by Darryl Ovens on Mon Jul 14 2014, 23:07

Yes I tried finishing with a polish type abrasive similar to brasso.  But still have a slow weep.

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Re: stopping a leaky fuel tap

Post by Andrew1971 on Thu Jul 17 2014, 19:10

Hi All
Now you have a nice clean taper there should be a spring that pulls the tapered part into the tap make sure it is still strong enough. That's how I got my petter a1 to stop leaking.

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Re: stopping a leaky fuel tap

Post by Darryl Ovens on Thu Jul 17 2014, 21:15

A common practice with conical or wedge type valves when they leak is to give the internal male component, (ie usually the handle), a light tap to drive it further into the taper.  So that was one of the first things tried but no change and the taper does not move which is what made me start to wonder about an unlapped ring of the taper at the large end, or "ridge".

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Re: stopping a leaky fuel tap

Post by Darryl Ovens on Mon Jul 21 2014, 21:39

I was looking at another taper wedge type valve today and noticed (to my surprise), that in the way that valve was made a "ridge" in this valve would occur inside the small end of the valve body! So depending on the valve there are several different places where this could occur!

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Re: stopping a leaky fuel tap

Post by kevjhnsn on Tue Jul 22 2014, 01:42

i polish my taps up as said by others earlyer with valve and t=cut then to finish i medium emmory cloth the moving core 3-4 turns,wipe clean and the smear it with some thick oil or grease and reasemble again ,touch wood never had a dripping tap from this method,
think of the tap being like a piston and cylinder, we de-glaze/remove the shine of a bore, so the piston rings make a good seal again, and less compression gases are lost if you see were im going here
hope this helps and works for you like it does for me
kev
p.s the give it a tap with hammer is also a way to slow things down on the drip to trickle states, but do it in the closed and open possitions only if needed

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