Fuel tap seal failure

Information relating to the Matchless G12 or AJS Model 31 650cc twin
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ixonchitts
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Fuel tap seal failure

Post by ixonchitts »

Hi,
I recently refuelled with a brand I've never used before (although fairly widespread in the Highlands and Islands) whilst on a tour of the outer Hebrides. Within 24hrs both main and reserve fuel taps began leaking badly. I've never had a problem with them during the two years I've had the bike although I don't know how old the seals are. Could it be a coincidence and I was just unlucky or has anyone else encountered similar problems? Could vibration cause them to fail -it was the first extended ride I've had since I got the bike?
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Rob Harknett
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Re: Fuel tap seal failure

Post by Rob Harknett »

If there are any features on the taps where you could tighten or loosen the washers, then vibration could make them leak. Depends what taps you have. The type with flat washer top and bottom of the on/off slide could loosen. Pull on type with barrel cork could loosen, if you have the old type fitted with a screw, you can tighten to compress the cork. Repros usually have corks riveted so you cannot replace them, buy new tap instead. Maybe the bike had just stood too long, taps sized a bit. petrol and vibes got to work loosen them. Check for anything loose, adjust corks/washers if you can, or replace, That should be the end of the problem.
ixonchitts
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Re: Fuel tap seal failure

Post by ixonchitts »

Thanks for the advice Rob, they are the pull on type. I hope to get a chance to examine them in detail tomorrow.
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Rob Harknett
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Re: Fuel tap seal failure

Post by Rob Harknett »

If they are like the old type, undo the side screw and pull the plunger out. The barrel washer may be held on by a screw. Tighten a little to compress the cork a bit. If you have very little petrol in the tank, perhaps lay the bike over with the footrest on a 3" high brick. So no need to drain the petrol. I have seen replacement plungers on e bay, not sure if they will fit, or perhaps fit loose and leak. don't loose the special little screw that holds the plunger in. There's like a little peg on the threaded end. that runs in the groove of the plunger. If the cork barrel shape washer is removal, replacement's are available. They may be dry, soak in petrol overnight to expand them.
56G80S
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Re: Fuel tap seal failure

Post by 56G80S »

If you you do lose or damage in removing the small screw that holds the plunger in place Rob posted a diagram of it which I used to make one up - should show up on a search - Ewarts petrol tap - size of small screw.

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ixonchitts
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Re: Fuel tap seal failure

Post by ixonchitts »

Mine are clearly repros with the barrel washer welded on. I take your point 're replacement plungers and the possibility that they may not be a good fit. I'm going to go the whole hog and replace both taps.

Thanks again for your advice.
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Rob Harknett
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Re: Fuel tap seal failure

Post by Rob Harknett »

AHH They make them not adjustable so you cannot compress the cork when worn or replace it. So you need spare taps or plungers instead of washers. They are not even worthy of the repro title as they are not reproductions of the original item. If getting new taps it may be worth checking if you can just replace the washer. If they do not, they will not be good value.
G15 Roy
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Re: Fuel tap seal failure

Post by G15 Roy »

ixonchitts wrote:Mine are clearly repros with the barrel washer welded on. I take your point 're replacement plungers and the possibility that they may not be a good fit. I'm going to go the whole hog and replace both taps.

Thanks again for your advice.
A photo would help to decide if repros or not because if you have original taps they are to good too waste.
Roy
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Rob Harknett
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Re: Fuel tap seal failure

Post by Rob Harknett »

G15 Roy wrote:
ixonchitts wrote:Mine are clearly repros with the barrel washer welded on. I take your point 're replacement plungers and the possibility that they may not be a good fit. I'm going to go the whole hog and replace both taps.

Thanks again for your advice.
A photo would help to decide if repros or not because if you have original taps they are to good too waste.
Good point. See below.
Ashampoo_Snap_2017.09.18_19h47m14s_004_.png
Note the long part that holds the cock washer that screws into the round disc. Some one may had punched the threaded end to stop the disc coming off. So it appears to be riveted. I have adjusted up corks until quite a bit of thread is seen. So once adjusted and tested they do not leak, punched the end to stop the disc coming off before finale fitting. Had these disc's coming off due to damaged threads years ago in my teens. Soon fixed by hitting the tap with a brick.
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