Britbike forum Forums British Motorcycle specific Brands Triumph bulletin board gas tap washer/seal

Hi David,


With respect, simple observation says this isn't correct for Stat-O-Seals:-

. You've posted in the past that you can tell the difference between the 55-degree and 60-degree angles on threads. I can't but a correctly-sized Stat-O-Seal should be screwed on to the thread, because I can see the "extruded into the threads" described by Richard.

. Then, when the Stat-O-Seal is compressed by the plain steel washer and tap locknut, where's the seal going to extrude to, being constrained by the steel washer, the tank and the steel or ally of the washer surrounding the seal itself?

I've seven fuel taps that standard Triumph parts have sealed at least for well over a decade and a couple exceeding four. The vast majority of Triumph owners I know and have known would be surprised their fuel taps don't seal using standard Triumph parts. Certainly I've never had to go looking for a 1/4"BSP Nyloc nut, even if such a thing exists?

Perhaps it's as "RPM" has suggested, the OD of many taps sold in the US is too-much smaller than the 1/4"BSP major and minor diameters? Perhaps dealers are supplying correct 1/4"BSP Stat-O-Seals but these taps could do with M13 or M12 Stat-O-Seals?

Hth.

Regards,

Hi, Parker makes a seal specifically for threads such as our fuel taps are. It's called thredseal. 1/2-13 size is very close to 1/4-19 BSP of our taps. It must be wound on.

The also make a stato seal with a thicker rubber, meaning the ID of the rubber is smaller so it presses much tighter on threads. It indeed must be wound onto tap. This one is not obviously listed in catalog.

I have 2 samples of each in my possession, as well as the regular stato seal the Triumph. parts places in USA sell.

Here's a link to the Thredseal page.

https://www.industrialseal.com/threadseals-parker.html


Here is another type that is supposed to seal threads. This one looks much more like the original Triumph to me. But never seen one in real life.
Available in either viton or Buna. BSP sizes.

https://www.discounthydraulichose.com/Bonded_Seal_Buna_BSP_Metric_p/9500.htm

Don

Hi Hillbilly, I really don't know the exact differences in California gas.

Unless you go to race gas station which is still unleaded, the highest octane is 91.

We also have winter & summer fuel. The switchover dates are set by the regulators of emissions & it is set by the calendar, not ambient temperature day to day or month to month. It's on this day the fuel from refinery changes. So with a small selling station the fuel could be way out of season. The way the bikes start is different with each fuel. I tend to find in a warm snap, winter fuel starts harder. In stop & go traffic 105f the fuel can boil in float bowl & won't idle. You have to keep blipping throttle to keep it running. Takes only a few minutes of 20mph to cool carb, then ok. Hot starts often require a good 5 second tickle, then hold full throttle.

In many states the octane is 93.

I have no idea the why we have only 91. So far as I can tell we have a minimum of 10% ethanol in fuel. I have never seen non ethanol unleaded fuel sold in CA.

I know from personal experience with my Mercedes 2000 E320 I reliably get 2-3 more miles per gallon with 93 octane. If I go from 91 to 87 California fuel I will loose 2-3 miles per gallon. The owners manual states use premium fuel.

The runs looses noticeable power up hill 87 to 91. Oddly 91 to 93 power seems the same, but mileage is consistently better with 93.

Looking at actual values in laptop the knock sensors backs off timing about 14deg with 87 compared to 91. The motor sounds different & feels like it's straining with timing backed off. I don't know what timing does with 93.

I've never ridden my bike with 93 so I have no idea how it would start & run on 93. From my car experience I'd say better.

Again I don't know why we don't have 93 & what does out of state 93 have in it that gives better mileage? Obviously it has more BTU or something per gallon, but what?

I'm 66. Back when I was 10 years old or so the smog was so bad in Los Angles to Pasadena it looked like it was a foggy day. Except the fog had a yellow brown tint to it. Burned your eyes, nose, throat. You could not see road signs 1/8 mile away. This was not uncommon or usual back then. Now it's rather rare to have smog like that there. So whatever the gas has in it as well as the emission controls it's working pretty good. The thing is our old bikes don't work so well on it.

Don

Hi Don,


Nope, 'fraid nothing like it at all, because that's a Dowty.

If you look closely at any Dowty, the cross-section of the seal itself is basically C-shaped, with the ends of the "C" forming two tiny lips; in the original designed use as a seal on the telescoping legs of aircraft undercarriages, the lips seal on the inner shaft as inner and outer move relative to one another.

If a Dowty seals on a thread, that's luck, because the seal is barely thicker than the washer itself; there is virtually nothing that can be compressed/deformed/extruded if a Dowty is between, say, a tank and the steel washer on a standard lever fuel tap.


Images of Stat-O-Seals have been posted and linked in threads numerous times, both here and in other Britbike internet forums. The Triumph part number for the Stat-O-Seal washer is 70-7351, called "Tap seal" in the parts book for your '73 TR7RV. Enter that part number plus "triumph" into your preferred internet search engine and any number of images will be displayed; e.g. here they are displayed on The Bonneville Shop's website with the 83-0002 plated steel "Washer[s]" that fit between the Stat-O-Seals and the tap locknuts.

Two other things to note in the TBS image:-

. The correct 83-0002 plain Washers are the same 7/8" OD as the 70-7351 "Tap seal" Stat-O-Seal washers; afaict, the plain Washers were/are sourced specifically for this feature and application as standard 1/2" i.d. washers are 1" o.d. Any "Dowty" washer fitting the 1/4"BSP tap thread would have an obviously-smaller o.d. than the plain Washers.

. The apparent 'star shape' of the outside edge of the black seal itself is specifically characteristic of a Stat-O-Seal. Dowty washers are also known as "bonded washers" because the seal is bonded to the metal of the washer; otoh, Stat-O-Seal seals are not bonded to the metal of the washer, careless fitting or removal can cause the seal to detach from the serrated i.d. of the metal.

One other feature of a Stat-O-Seal not visible in that image, but visible in earlier linked images is the seal is relatively much thicker than the metal; otoh, a Dowty seal is pretty-much the same thickness as the metal - why I posted above, "there is virtually nothing that can be compressed/deformed/extruded if a Dowty is between, say, a tank and the steel washer on a standard lever fuel tap". Therefore, one useful specific property of a Stat-O-Seal is the metal part will not scrape tank paint when the tap nut is tightened; :bigt otoh, there isn't anything to stop a Dowty doing so.

Hth.

Regards,

On vehicles with modern electronic engine management and detonation sensors,the timing can be advanced on the higher octane...This is especially where a premium fuel is recommended.If the ECU retards timing for lower octane ,then power will fall off a bit, usually noticeable....Generally speaking,more advance give better fuel mileage at part throttle.....
You have a portable scanner that displays fuel trims,timing advance, etc? Plug it in and drive around for awhile to observe what goes on...

So, back to the original question, what is the best seal, best way, best of whatever to install the fuel taps...LOL

I suspect the use of Stat-O-Seals in this application was another of those later “what can we find that will just about do the job” solutions.

Quite why the relationship between tank boss and tap changed (most through history just fitted by winding in tightly, with a fibre sealing washer, and you could get the correct orientation of the tap by different tightening and/or different washer thickness).

For whatever reason (perhaps they didn’t want to waste time orienting the boss correctly when welding the tanks?) this adjustable system was employed, with locknut, washer and seal. Which introduces the thread sealing issue, which never existed before the apparent need for adjustable fuel taps.

Stat-O-Seals are not designed for thread sealing. They are essentially similar to Dowty washers, in that they seal surface to surface (eg bolt head to banjo in hydraulics). That the compression of the rubber may close-up on the (usually) smooth bolt shank is not important for its function. They are in effect, captive “O rings”, without the need for machined recesses for the rings.

Such seals have been used in hydraulics for many years, at 10’s of thousands of PSI, but never to seal threads, and I don’t know why we keep talking about aircraft undercarriages, that is but one application, and not in terms of sliding piston situation, an entirely different seal requirement.

If a Stat-O-Seal works in the petrol tap scenario, it does so by bodge, not design.

As has been described, it must be so undersized that it must be threaded on, and thus already half filling the threads, so that compression completes the filling of the threads (hopefully).

The star shape of this seal is more than just a star shaped rubber in a star shaped washer, the rubber is crimped between the metal layers to hold it securely in place (possibly the reason for its name?). One of its principal benefits is that it is less likely to come apart than a merely bonded seal.

If TR7’s suggestion of Thredseals had been available in the day, I think they would have been a proper solution, and maybe nowadays, if available in small numbers.

Dowty or Stat-O-Seals were never intended to be screwed onto their Fasteners, what a tedious production step that would be.

Yet I wouldn’t argue with the experts here that Triumph used them for this purpose regardless!

If something does the job it is not a bodge but a proper engineering solution.
Engineering is the art of making things work.
Just my two cents worth of course.

Hmmmmm? ,
Well with 45yrs + of sealing up boilers / gas & heating pipes and all thing else wet 'n' screwed .. i know what i'd be using
Looks like the perfect opportunity to prove how good those Doubty washers are and let us all know ? :bigt

Hi Dave,


You are confused. Whatever you're looking at, or have looked at in the past, it isn't/wasn't a Stat-O-Seal. Nothing on a Stat-O-Seal is "crimped", there aren't any multiple "layers".


But, if you're confused about what a real proper Stat-O-Seal washer looks like, you can't appreciate all the functions it performs in the position used by Triumph and BSA. Details of all those functions have been posted but you choose to ignore those descriptions?


:bigt


This is nonsense. The thread doesn't start in the same place on every tap so how would "orienting the boss correctly when welding the tanks" work?


This is nonsense. What do you suppose the fibre washer on the 82-1717 tap does?




Because, if you had read what had been posted previously, you would know that the "Dowty" seal is so called because it was invented by the company of that name when the company was developing telescoping aircraft landing gear suspension.


You have not understood what has been posted. There is no "must" about threading them on to the tap, particularly if you know you have a correctly-sized Stat-O-Seal and thread; I very much doubt Meriden or Small Heath workers threaded them on to the taps but that was forty-plus years ago. Today, especially where everything has been 'metric' for decades and cheap parts are bashed out without reference to standards, not everyone always knows they have a correctly-sized Stat-O-Seal and fuel tap thread; but we aren't on piece-work and a damaged Stat-O-Seal is more time-consuming than the precaution I described just because I happen to use it.


As I say, you are confused; whatever you're looking at, or have looked at in the past, it isn't/wasn't a Stat-O-Seal.

As I say, nothing on a Stat-O-Seal is "crimped". The metal part has a series of specially-shaped serrations around its i.d.; the "star-shape" I mentioned is the pattern made by the visible ends of the serrations in the image I posted; the ends of the serrations are not always visible on every Stat-O-Seal.

I suspect the seal itself is moulded around these serrations because, if the seal becomes detatched from the metal part, I've never been able to refit it, which suggests the seal isn't moulded separately and then pressed on to the metal part. Therefore, this particular property of a real Stat-O-Seal is of no benefit whatsoever compared to "a merely bonded seal".

Hth.

Regards,

Hi Mark,


In my experience, exactly what it says in the parts book:-



If you feel the need to wrap PTFE tape around the fuel tap threads, it's your bike.

Hth.

Regards,

Thanks Stuart, your remarks inspired me to look into the subject in more detail.
As I’ve only had cause to use “ordinary” fuel taps, I’ve not had to deal with this issue.

“This is nonsense. What do you suppose the fibre washer on the 82-1717 tap does?”

It seals the surfaces of tank to tap, it does nothing to seal threads. That is a conventional flange fitting tap, the type used for donkeys. Such a design has no need to seal the threads.

You are correct, I was wrong to think that there was some sort of crimping involved in the Stat-o-Seal, I must have been thinking of something else I’ve seen.

Though I suspect that the statement:

“f you look closely at any Dowty, the cross-section of the seal itself is basically C-shaped, with the ends of the "C" forming two tiny lips; in the original designed use as a seal on the telescoping legs of aircraft undercarriages, the lips seal on the inner shaft as inner and outer move relative to one another.”

is misleading, as Dowty seals were not the sliding seals within the hydraulic cylinders, but the static seals in hydraulic pipe unions. The intention was to provide a more reliable/re-usable washer than the usual copper or aluminium.

Both Dowty and Stat-o-Seals were designed for similar applications, where the compression of the rubber would force it against the plain shank of the bolt. Even this wasn’t essential, because the compression of the rubber between the surfaces provides a reasonable seal at moderate pressures, but to perform to design pressures it needs to be compressed against the correct size plain shank.

To stand a hope of sealing on a thread, it must be smaller than the nominal diameter of the thread to begin with, so that the compression can fill to the bottom of the valleys. I would agree with your technique of winding it on because of this straying from design intention.

I also hazard to think that the washer that goes with the seal has an ID closer to the thread diameter of the tap than any average washer may have, to ensure that it exerts pressure on all of the rubber without any “escape” gap.

"Therefore, one useful specific property of a Stat-O-Seal is the metal part will not scrape tank paint when the tap nut is tightened; otoh, there isn't anything to stop a Dowty doing so.”

I’m unsure what this means, both types should seal against flat, clean metal surfaces, not paint, and both are intended to be clamped metal to metal to metal.

Another’s comment:

“If something does the job it is not a bodge but a proper engineering solution.
Engineering is the art of making things work.”

I think is rather generous towards bodges. That several contributors have had problems with this arrangement, which should be a simple matter, does suggest that it lacks a certain “properness” as an engineering “solution”.

As I mentioned, PTFE paste in the tube.... You can see it on the gas tap fittings and where i wiped my finger on the fuel tank on my race bike, NPT threads made up wrench tight, no leaks.. ..Of course it's not pump urine but leaded race fuel..

IMHO all that's needed to seal petrol taps to the tank is a simple fibre washer that has the same internal diameter as the tap threads.

What is important is to ensure that the tank outlet flange is flat to ensure a good seal and that no paint present and that the tap has a nut fitted to tighten against the fibre washer.

Previously I have tried Dowty washers but never had any success. The problem as pointed out above is that Dowty washers are intended to seal against an internal smooth surface not a thread, furthermore the steel body does not easily crush and seal against the tank outlet flange and therefore is prone to leaks.

if you stop fuel at the threads the washer is doing little, plumbers tape is SOP for me, after that a fibre washer and a thicknessed steel washer so the tap clocks in where you need it. Select steel washer to clock in. Chances of a new cheapo tap fitting an old tank or new tank well are slim, even a decent quality item will be a bit undersized just to make sure they screw in.
i dont consider this a bodge ,its std practice for most hydraulics especially for this type of fitting, plumbers tape is good stuff. Dont go mental and keep it neat .
have used "Dowties" in the past and they work just the same as fibre washers, look a bit neater ,