T: Fuel Tank Petrol tap corks and Ethanol

oexing

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The cone type taps all got same problem: You cannot run same material in itself, brass in brass will seize, like plain steel in plain steel or alu in alu. You´d have to do a mod either by plating one component - the cone here - or find a grease that will last with fuel, so no seizures then.
I went for ss cone in brass body because I can do it all at home. A great alternative may be hard chroming the cone and lap it afterwards but costs will rocket I guess.
As to fuel resistant grease I have no idea. Does anybody have a truly long time experience with that kind of stuff and in what application ?
The typical plain seal/gaskets of fuel taps with two or three holes in the gasket were made from rubber type material which is no longer fuel resistant. I changed them with home made cork gaskets, delicate to do but work allright then, cork has no problem with alcohol, but possibly water and biological life in fuel .
. Once the seal in those is leaking you can do the cork mod. Big drawback with cork is you´d have to drink several bottles of quality wine or brandy to get suitable corks for making tap seals from them - oh well, you will accept some sacrifes in life and will have done so in the past I guess . . . .
Coincidentally I had to overhaul both taps on the 1935 Guzzi GTV yesterday for the MOT. The springs in the 1/8" pipe thread taps were very strong so the soft cork was pressed so much till the two cast-in tubes got proud and kept the mating faces apart, leaks then. Made softer springs and new corks so this should do longer than one year as with last corks and hard spring.

Vic

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LoneStar

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I've had good experience with this very cheap solution, which also preserves the original appearance:


They are a bit thick, causing stiff operation, but easily sanded down for a better fit.
 
G

Graham Smith

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I was led to believe someone in the Club was having a batch of neoprene 'corks' made which were a direct replacement for the originals.

These are supposed to outlast the rider!
 

TouringGodet

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I recently fitted the o rings too, same results, they are a bit oversize on the OD. I like the item in the picture posted by Ian above. Viton or neoprene, if they are sized correctly to seal, but still slide without too much force required, they appear to be ideal. The o rings have to be compressed a bit lengthwise by the adjustable plunger to avoid leaks, which causes them to squish out on the OD. Even when loose, the plunger with o rings is hard to assemble into the tap. I hope these other ones will allow the same adjustment of the plunger to find the optimum sweet spot between leaking and being too snug to slide, and be easy to assemble, then use the adjustment to snug them up.
 

oexing

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I´d be very surprised if neoprene was not affected by modern gasoline. The typical NBR o-ring will swell in auto fuel so Viton will be the best bet for the plunger type tap. Any swelling material will most likely not give smooth action in the tap. Please do your own test and throw an o-ring or seals you fit in engines or gearboxes for output shafts in a jar with auto fuel, E 10 or super plus, does not matter (it is NOT the alcohol to be critical really) and wait a few days . You will see that all sizes will have grown a lot so a shaft seal lip will no longer be tight on the shaft it was designed for. When you wait a few days all NBR items will dry on air and sizes will return.

Vic
 

greg brillus

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I tried some of those o ring mods that were available from the states years ago, and found i had to replace all of them........the o rings get guillotined from passing the sharp edged holes through the tap assembly........they may not leak externally but will leak internally causing the stock carby's to constantly drip fuel.......not too good on a freshly painted shadow engine.
 

Cyborg

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Looking at one of my taps, there would only be about one O-ring’s worth of distance before fuel started bleeding past into the float bowl. So if there was any damage on the most inward O-ring it would leak internally. That one Ian posted looks like a much better idea.
 

Roslyn

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Looking at one of my taps, there would only be about one O-ring’s worth of distance before fuel started bleeding past into the float bowl. So if there was any damage on the most inward O-ring it would leak internally. That one Ian posted looks like a much better idea.
you could try using a section of cord instead of o-rings i have not done this yet but using corks for me works atm and is cheap to repair
 
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