T140V Fuel Petcocks - and the goofy "reserve" selection . . .

[Lordmac]

The situation: Triumph fuel tanks are built so there are fundamentally two halves separated by a tunnel which mounts to the large frame tube.
Imagine if you will, the two fuel petcocks that come stock (see photo below so you don't have to imagine) on most US import T140V Bonnevilles. Visualize that the one marked "reserve" is on the left side of the tank and the main (with that little extension tube rising up) is on the right side. Now imagine that you just ran out of fuel (on the main, or right side), and now you switch to the left "reserve" side and fuel then flows to the carbs. Okay, what about that fuel that remains in the right side of the tank which cannot flow out because the extension tube limits it? There is no balance tube under the tank which connects the right side to the left so that fuel can be used as reserve. The fuel now trapped in the right side only can be used if you get off the bike and tilt it over so the fuel can drain across to the left.

The question: How come they make petcocks that do that? I mean, is that dumb, 'er what? If there were a balance tube under the tank which connects the two sides, then the extension tube on the main petcock would make sense. But without such balance tube, in my opinion, both petcocks should drain all the fuel on their respective sides. Does anybody have a tank different than the one I have?

 

[Rudie]

Replace the taps in your photo with the Paioli type fitted to the Triumph tanks made in Italy in the 1980s, both taps have main and reserve.

Original Paiolis (60-7508 and 60-7509) fitted to tanks with 1/4"BSP threads each required a 'male-male adaptor' (83-7970) as the tank threads are female and so are the tap threads - an adaptor has a 1/4"BSP male thread on one end, M16 x 1.0 thread on the other end. Each tap-adaptor combination also requires a 00-0075 sealing washer between tap and adaptor.

Or there are 'Paioli-type' left- and right-hand taps with 1/4"BSP male threads.

Or, 83-7970 and 00-0075 obtained, much cheaper (certainly in the UK) are Italian BAP taps sold for the large capacity air cooled Moto Guzzi twins.

Btw, if the taps in your photo are also on your bike, they are not the originals. The ones in the photo are based on ones NVT obtained originally for the T160 from late 1974 then subsequently fitted to all 76 on twins until replaced by the Paiolis. The main difference between the ones in the photo and the NVT ones is the plate on the reserve tap was above and to the left of the lever - taps mounted on the tank, both levers pointed in the same horizontal direction in the off position.

Not sure why the pattern makers did not simply make the reserve tap the same as the original?

 

[Lordmac]

Btw, if the taps in your photo are also on your bike, they are not the originals.

Hey Rudie:
Yeah, the taps in the photo are ALMOST exactly like the originals on my bike. I shall explain;
The original petcocks (which I still have) equipped on my 1978 T140V (that I bought new in May of 1978) have . . . nylon shaft/valves which eventually broke on each one causing replacement with the ones shown in the picture that have brass shafts/valves and reverse-direction flags, but otherwise are pretty-much the same. I always thought, as I was tilting my bike over to get the fuel from the right side to the left, that there was something very strange about that situation. I will take a look at the taps you have mentioned and perhaps install a set of those. In the mean time, before I installed the replacement taps, I removed the extension tube from the 'main' tap so I could at least use the fuel from the right side. But, problematically, there is very little reserve capacity from the left side alone.

 

[Lordmac]

I will take a look at the taps you have mentioned and perhaps install a set of those.

I am replying to myself here, so . . .
I found a set of the taps and the adapters that Rudie mentioned (see photos below just for clarification) and thought these just might do, and for only about a hunnert bux! The only problem with these is . . . they aren't o-ree-jenny! And, my Bonnie might reject them . . .

 

[Rudie]

I shall explain

No need, I owned my T160 from brand new; as I posted earlier, NVT first sourced the original taps for the T160.

I found a set of the taps and the adapters that Rudie mentioned
only problem with these is . . . they aren't o-ree-jenny

The pattern brass shafts/valves will fit in the bodies of your bike's original taps. The reserve tap plates require a small section removing from the circular part of each plate, so the pattern plate can be removed and the original plate fitted to the brass shaft/valve; the missing section of the plate is hidden by the circlip positioned judiciously.

my Bonnie might reject them

Adapters and BAP taps not rejected by my T160 for several decades. Thankfully still much less than "a hunnert bux" here even today (hopefully not that nice Mr. Trump's import tariffs ).

 

[LoneRanger]

The situation: Triumph fuel tanks are built so there are fundamentally two halves separated by a tunnel which mounts to the large frame tube.
Imagine if you will, the two fuel petcocks that come stock (see photo below so you don't have to imagine) on most US import T140V Bonnevilles. Visualize that the one marked "reserve" is on the left side of the tank and the main (with that little extension tube rising up) is on the right side. Now imagine that you just ran out of fuel (on the main, or right side), and now you switch to the left "reserve" side and fuel then flows to the carbs. Okay, what about that fuel that remains in the right side of the tank which cannot flow out because the extension tube limits it? There is no balance tube under the tank which connects the right side to the left so that fuel can be used as reserve. The fuel now trapped in the right side only can be used if you get off the bike and tilt it over so the fuel can drain across to the left.

The question: How come they make petcocks that do that? I mean, is that dumb, 'er what? If there were a balance tube under the tank which connects the two sides, then the extension tube on the main petcock would make sense. But without such balance tube, in my opinion, both petcocks should drain all the fuel on their respective sides. Does anybody have a tank different than the one I have?

Pretty sure the originals on my '72 TR6R didn't have an 'extension tube' so, as you say, one half of the tank served as reserve.

 

[Rudie]

Pretty sure the originals on my '72 TR6R didn't have an 'extension tube'

All original 'main' taps had the 'extension tube' inside the gauze filter.

 

[Lordmac]

The pattern brass shafts/valves will fit in the bodies of your bike's original taps.

Seriously? I never would have guessed. Good thing I keep ALL of my old parts. I shall then build myself a set using my original tap bodies just so I can get the extra concours d'élégance points. Thanks for that, Rudie!

 

[Lordmac]

Pretty sure the originals on my '72 TR6R didn't have an 'extension tube'

If they didn't, would that be a surprise? Triumph seemed to be in the habit of using whatever was on hand in those days and "forgot" to include changes in the parts manuals, I read in a book by some Triumph book writer.

 

[Lordmac]

Adapters and BAP taps not rejected by my T160 for several decades. Thankfully still much less than "a hunnert bux" here even today

I was slightly surprised at the price of those taps . . . anywhere from thirty-five to fifty US dollars each, no matter where they are coming from. And the adapters are pretty much fifteen apiece . . .

The original "style" taps aren't any cheaper, though . . .

Gosh, my like-new Bonnie must be worth a gazillion dollars by now . . .

 

[Rudie]

Pretty sure the originals on my '72 TR6R didn't have an 'extension tube'

If they didn't, would that be a surprise?

Pre T160, generally the taps are identical except the 'main' tap has the "extension tube". If @LoneRanger bought his bike new, either the production line or the dealer fitted a reserve tap in place of the correct/original main tap. Otoh, if @LoneRanger did not buy his bike new, in addition to production line or dealer(s), a previous owner could also have fitted a reserve tap in place of the original main tap.

The only other difference I have seen between a few pre T160 main and reserve taps is "R" stamped on the lever of the latter.

Triumph seemed to be in the habit of using whatever was on hand in those days and "forgot" to include changes in the parts manuals, I read in a book by some Triumph book writer.

Sadly, there is a long and still growing list of errors in books and magazines ... Book and magazine writers are by definition not production planners or senior managers of large manufacturing plants - Meriden was not some quaint cottage industry, the factories (note plural) assembled hundreds of bikes every week, that cannot be done "using whatever was on hand". Meriden built in batches, planned up to a year in advance based on British dealer and foreign importer orders. Components could be changed between batches, from modifications, feedback from earlier batches and/or importer requests. The parts manuals available today are generally copies of what Meriden produced for the start of a model year; what are mostly not available today are the typed manual update sheets sent regularly throughout a model year to every dealer around the world. Involved with Triumphs for nearly fifty years, I never knew a new bike with two reserve taps.

only about a hunnert bux

I was slightly surprised at the price of those taps . . . anywhere from thirty-five to fifty US dollars each, no matter where they are coming from. And the adapters are pretty much fifteen apiece

$15 for an adaptor is only a little more than the UK price. Otoh, this British Moto Guzzi spares dealer, scroll down to "Fuel Tap LH | TAA17105A" and "Fuel Tap RH | TAA17105B" (are what I use), note just over £10 (ten pounds, 13 bucks according to Google) each ... unlikely p&p to the US will be anywhere near $40-odd ...?

 

[Lordmac]

Meriden was not some quaint cottage industry, the factories (note plural) assembled hundreds of bikes every week, that cannot be done "using whatever was on hand".

And in defense of Meriden and their sage designers, engineers and builders (if it were warranted) most every part (bit) I ever searched for by part number from the parts catalogue, has garnered the correct parts for my Bonneville.

I have, however, had experiences where part numbers for certain parts are not shown in the catalogue, or are inaccurate. In example, my '78 catalogue lists the gasoline tank for my US version as: 83-7113, Tawny Brown and Gold, T140V, 3.6 US gallons, but it is a 2.5 gallon tank. Other publications such as the owner's manual list it as a 2.5 gallon tank.Or, in some brochures it indicates 2 Imp gallons (2.4 US) Overall, though, I have no complaints. In fact, I am a stickler for using OEM parts (cost, what cost?) and am very pleased with owning and maintaining a Meriden machine.

 

[Rudie]

part numbers for certain parts are not shown in the catalogue

Part might have been supplied with another part? E.g. a regular one today is the wiring grommets in headlight and oif do not have a number in the parts book, because then they were supplied by Lucas with the wiring loom; today, they do have a separate part number, simply ask a dealer, write the number in your parts book for future reference.

part numbers
are inaccurate. In example, my '78 catalogue lists the gasoline tank for my US version as: 83-7113, Tawny Brown and Gold, T140V, 3.6 US gallons

"Meriden Misprints". Parts books were only ever intended to help dealer staff find parts for customers. Because the books were supplied to dealers either free or at very low cost, the books were produced as cheaply as possible. If 83-7113 produced an identical Tawny Brown and Gold tank as the one to be replaced on the customer's bike, who cares the capacity is misprinted in the 78 parts book? So time was not spent over every piffling, irrelevant detail; if something needed correcting, it would have been in an update sheet. "3.6 US gallons" is simply a hangover from the earliest oif tanks, based on the pre 71 TR6R tank shell afaict.

 

[Bloodknot]

For parts books and workshop manuals for the Meriden machines and a whole lot more you need to have a look at this. As you will see it’s not expensive and has more information about your Meriden machine than you will ever need. FYI my pre-unit Tbird had a single Monoblock carb with both taps joining to a single union that bolted onto the carb so when I had the head gasflowed with larger valves I fitted a pair of Concentrics with each carb supplied by the tap on it’s side of the tank and a link pipe between the two carbs so that both carbs could be fed by one of the taps on either side of the tank. Neither taps had the header tubes so you could choose which tap was your reserve.

 

[CarlS]

For parts books and workshop manuals for the Meriden machines and a whole lot more you need to have a look at this. As you will see it’s not expensive and has more information about your Meriden machine than you will ever need. FYI my pre-unit Tbird had a single Monoblock carb with both taps joining to a single union that bolted onto the carb so when I had the head gasflowed with larger valves I fitted a pair of Concentrics with each carb supplied by the tap on it’s side of the tank and a link pipe between the two carbs so that both carbs could be fed by one of the taps on either side of the tank. Neither taps had the header tubes so you could choose which tap was your reserve.

Thanks for the link.